Arrayed waveguide grating, arrayed waveguide grating module, arrayed waveguide grating module waveguide compensation method, optical communication system

ABSTRACT

An arrayed waveguide grating  101  is shown, which comprises at least one input waveguide  103 , a plurality of output waveguides  104 , at least one wavelength compensation output waveguide  105  disposed adjacent to the output waveguide  104 , a channel waveguide array  107 , an input side slab-waveguide  108 , and an output side slab-waveguide  109 . The wavelength compensation output waveguide  105  has a tapering connecting portion connected to the output side slab-waveguide  105 . Thus, the outputted light has a sharp spectrum, thus permitting ready wavelength compensation.

The present Application is a Divisional Application of U.S. patentapplication No. 10/001,812 filed on Dec. 5, 2001, now U.S. Pat. No.6,690,861.

BACKGROUND OF THE INVENTION

This application claims benefit of Japanese Patent Application No.2000-371434 filed on Dec. 6, 2000, the contents of which areincorporated by the reference.

The present invention relates to arrayed waveguide grating, arrayedwaveguide grating module, arrayed waveguide grating module waveguidecompensation method, optical communication device and opticalcommunication system and, more particularly, to the arrayed waveguidegrating, which permits ready selection of wavelength to be used, thearrayed waveguide grating module using such arrayed waveguide grating,the arrayed waveguide grating module wavelength compensation method ofcompensating in the arrayed waveguide grating module and the opticalcommunication unit and the optical communication system.

In optical fiber communication systems, further transfer capacityincrease has been called for together with transmission data capacityincrease. In DWDM (Dense Wavelength Division Multiplexing), theimportance of the optical wavelength filter asmultiplexing/demultiplexing device for multiplexing and demultiplexingwavelengths has been increasing.

Optical wavelength filters are of various types. Among the opticalwavelength filters, the arrayed waveguide gratings have narrowwavelength characteristic and high extinguishing ratio, and they furtherhave features as multiple-input multiple-output filter device. Thus, theoptical wavelength filters capable of demultiplexing the multiplexedsignals and performing inverse operation, and thus it can readilyconstitute a multiplexing/demultiplexing device. By using quartswaveguide for the arrayed waveguide grating, it is possible to obtainexcellent coupling to optical fiber and realize low insertion lossoperation with an insertion loss of several dB (decibels). The arrayedwaveguide grating has attracting attention as particularly importantdevice among the optical wavelength filters, and its extensive home andabroad researches and investigations are in force.

FIG. 18 shows the overall construction of a prior art arrayed waveguidegrating. The arrayed waveguide grating 10 as shown comprises, formed ona substrate 11, one or more input waveguides 12, a plurality of outputwaveguides 13, a channel waveguide array 14 curved in a predetermineddirection with different radii of curvature, an input sideslab-waveguide 15 inter-connecting the input waveguides 12 and thechannel waveguide array 14, and an output side slab-waveguide 16inter-connecting the channel waveguide art 14 and the output waveguides13. A multiplexed light signal inputted from the input waveguide orwaveguides 12 to the input side slab-waveguide 15 is expanded as itpasses therethrough and then inputted to the channel waveguide array 14.

The channel waveguide array 14 includes a plurality of arrayedwaveguides with lengths progressively increasing or decreasing by apredetermined waveguide length difference. The light signals passingthrough the these arrayed waveguides reach the output sideslab-waveguide 16 one after another by a predetermined phase differenceinternal. Actually, however, wavelength dispersion is present, and thein-phase plane is tilted independence on the wavelength. Consequently,the light signals are focused (i.e., converged) on different positionson the interface between the output side slab-waveguide 16 and theoutput waveguides 13. With the output waveguides 13 disposed at thepositions corresponding to the respective wavelengths, it is possible totake out a desired wavelength component from the output waveguides 13.

In the meantime, in such arrayed waveguide grating 10, the wavelengthselection should be performed in conformity to the grid of the ITU(International Telecommunication Union). The wavelength of the arrayedwaveguide grating 10, by the way, is very susceptible to the refractiveindex changes of the waveguide material. This means that the centerwavelength as selected wavelength is subject to variations due tofluctuations in a film formation process as manufacturing process.Therefore, it is frequently impossible to obtain a value as desired.Also, the selected wavelength variation poses a problem that the opticalloss with the wavelength in use is increased. Accordingly, it has beenin practice to do wavelength compensation to a proper value by somemeans after completion of the arrayed waveguide grating.

For example, according to Japanese Patent Laid-Open No. 9-49936 aninput/output waveguides for wavelength compensation are provided inaddition to the normal input/output waveguides based on AWG arrayedwaveguide, and are changed according to the wavelength compensationamount.

Denoting the demultiplication direction angle difference with respect tothe wavelength difference by δλ, in the arrayed waveguide grating it ispossible to compensate for the center wavelength λ_(in) by an amountgiven by the following equation (1) by changing the positions of theoutput waveguides 12, i.e., the slab incidence angle θ_(in).

δλ_(in)=(δλ/δθ).θ_(in)  (1)

The input/output waveguides, however, are disposed discretely.Therefore, the wavelength compensation amount is also discrete, and itis possible to obtain wavelength compensation as desired. In order toobtain the wavelength compensation amount as desired, it is necessary toset the slab incidence angle θ_(in) as desired.

According to Japanese Patent Laid-Open No. 2000-162453, the selectedwavelength center is shifted by irradiating an AWG array part withinfrared rays and thus changing the refractive index of the irradiatedart. According to P. C. Clemens et al, IEEE Photon. Tech. Lett., Vol. 7,No. 10, pp. 1040-1041, 1955 and Transactions of Institute of Electronicsand Data Communication Engineers of Japan, C-3-76, 2000, the selectedwavelength compensation is performed by changing the position of lightincidence on an input side slab-waveguide.

FIG. 19 shows the construction of an arrayed waveguide grating, whichdoes selected wavelength compensation by changing the position ofincidence of light on an input side slab-waveguide. In the proposal inthe above P. C. Clemens et al, IEEE, Photon, Tech. LETT., Vol. 7, No.10, pp. 1040-1041, 1995, the AWG wafer 21 of the substrate is severed atan input side slab-incidence part 22. The slab-incidence part 22 isreinforced with glass, and an input fiber 24 which is also reinforcedwith glass is bonded (i.e., secured by adhesive) to the slab-incidencepart 22. At the time of the bonding, the centering is performeddirectly, and the position of the input fiber 24 is changed as desiredin correspondence to the wavelength compensation amount.

FIG. 20 shows what is proposed in the Transactions of Institute ofElectronics and Data Communication Engineers of Japan, C-3-76, 2000.This proposal is different from the above structure described inconnection with FIG. 19, in which the input fiber 24 is bonded to theslab-incidence part 22. As shown in FIG. 20, an input fiber 31 isconnected via a slab-introduction optical waveguide 32 to the input sideslab-waveguide 33. The input and output side slab-waveguides 33 and 34are formed on an AWG element wafer 35, and a channel waveguide array 36is connected between these slab-waveguides. Output waveguides 38 areconnected between the output side slab-waveguide 34 and a fiber array37.

In addition to the above proposals, it is in practice to change thetemperature of mainly the channel waveguide array part (see channelwaveguide array 14 shown in FIG. 18) of the arrayed waveguide gratingand change the wavelength by adjusting the refractive index width athermo-optical effect thus obtained. To this end, a temperaturecontroller such as a Velch element or a heater is used.

When carrying out such arrayed wavelength grating wavelengthcompensation as to match the ITU grid by the above various proposals ormethod, such high accuracy compensation with an error of several pm(picometers) is required. This demand is on an increasing trend togetherwith the progress of the dense wavelength division multiplexing as notedabove.

FIG. 21 shows an example of the spectrum shape of the light signaloutputted from the arrayed waveguide grating. In the Figure, theordinate is taken for the light signal output level of the arrayedwaveguide grating, and the abscissa is taken from the wavelength. It isassumed that the same light signal output level has two differentspectrum shapes 41 and 42. Of these spectrum shape, the relatively sharpspectrum shape 41 shown by dashed curve is capable of readily detectingthe center wavelength. On the other hand, with the duller spectrum shape42 it is difficult to detect the center wavelength. This means that inthis case the accuracy of the center wavelength compensation isdeteriorated.

FIG. 22 shows a different example of the spectrum shape of the lightsignal outputted from the arrayed waveguide grating. Of the two spectrumshapes 43 and 44 in this example, although their light signal outputlevel integrals are equal, the spectrum shape 43 has a clear top, whilethe other spectrum shape 44 has a rather flat top. In order to reducethe loss variations in the ITU grid band as much as possible, a flat topshape such as the spectrum shape 44 is preferred. In this case, however,a problem is posed that the accuracy of the center wavelengthcompensation is deteriorated.

While problems in the arrayed waveguide grating have been discussedabove, the same problems are also present in the arrayed waveguidegrating module, optical communication device and optical communicationsystem using such arrayed waveguide grating.

SUMMARY OF THE INVENTION

An object of the present invention, therefore, is to provide arrayedwaveguide grating, arrayed waveguide grating module using such arrayedwaveguide grating and arrayed waveguide grating module wavelengthcompensation method used for wavelength compensation in such arrayedwaveguide grating module, which permit accurate center wavelengthcompensation of each waveguide in an arrayed waveguide grating, anarrayed waveguide grating module using such arrayed waveguide grating,an arrayed waveguide grating module waveguide compensation method usefor wavelength compensation in such arrayed waveguide grating module,and optical communication device and optical communication system usingsuch arrayed waveguide grating.

Various aspects and advantages thereof of the present invention whichwill be summarized as follows:

According to a first aspect of the present invention, there is providedan arrayed waveguide grating comprising: one or more input waveguides;an input side slab-waveguide connected to the output side of the inputwaveguide or waveguides; a plurality of arrayed waveguides formed on theside of the input side slab-waveguide opposite the input waveguide orwaveguides; an output side slab-waveguide connected to the otherterminal of the arrayed waveguides; a plurality of first outputwaveguides connected to the output side slab-waveguide on the sidethereof opposite the arrayed waveguides; and at least one second outputwaveguide formed together with the first output waveguides on the sideof the output side slab-waveguide opposite the arrayed waveguides; theafore-said components being all formed on a substrate and the secondoutput waveguide outputting an optical spectrum different from theoptical spectral outputted from the other output waveguides.

In this embodiment, from the second output waveguide or waveguides amonga plurality of output waveguide disposed on the output side of thearrayed waveguide grating, an output light signal spectrum differentfrom the output light signal spectra from the other output waveguidesare obtained, and they are used for center wavelength compensation ofeach waveguide of the arrayed waveguide grating.

According to a second aspect of the present invention, there is providedan arrayed waveguide grating comprising: one or more input waveguides;an input side slab-waveguide connected to the output side of the inputwaveguide or waveguides; a plurality of arrayed waveguides formed on theside of the input side slab-waveguide opposite the input waveguide orwaveguides; an output side slab-waveguide connected to the otherterminal of the arrayed waveguides; a plurality of first outputwaveguides connected to the output side slab-waveguide on the sidethereof opposite the arrayed waveguides; and at least one second outputwaveguide formed together with the first output waveguides on the sideof the output side slab-waveguide opposite the arrayed waveguides; theafore-said components being all formed on a substrate and a connectingportion of the second output waveguide with respect to the output sideslab-waveguide having a shape different from the shape of connectingportions of the first output waveguides with respect to the output sideslab-waveguide.

In this embodiment, the connecting portion of the output waveguidedisposed as second output waveguide among a plurality of outputwaveguides on the output side of the arrayed waveguide grating has ashape different from the shape of the connecting portion of the outputwaveguides as the output waveguides. By using these waveguides, thecenter wavelength compensation of each waveguide of the arrayedwaveguide grating can be performed appropriately by changing thespectrum shape or like means.

According to a third aspect of the present invention, there is providedthe arrayed waveguide grating according to one of the first and secondaspects, wherein the second output waveguide constituting the outputwaveguides is a monitor light waveguide for wavelength monitoring.

In this embodiment, the second output waveguide is used as, forinstance, a wavelength monitor.

According to a fourth aspect of the present invention, there is providedthe arrayed waveguide grating according to the first aspect, wherein thesecond output waveguide constituting the output waveguides outputs anoutput spectrum having a narrower spectral width than the spectral widthof the output optical spectra of the first output waveguides.

In this embodiment, the spectrum width of the spectrum of the lightsignal outputted from the second output waveguide is narrow compared tothe usual waveguides as output waveguides. It is thus possible toreadily specify the center wavelength, and the range in which errorsoccur is small.

According to a fifth aspect of the present invention, there is providedthe arrayed waveguide grating according to the first aspect, wherein thesecond output waveguide constituting the output waveguides outputs anoptical spectrum having a sharper peak than the peak of the opticalspectra of the first output waveguides.

In this embodiment, the spectrum of the light signal outputted from thesecond output waveguide has a sharp peak compared to the usualwaveguides as the output waveguides.

According to a sixth aspect of the present invention, there is providedthe arrayed waveguide grating according to the second aspect, whereinthe second output waveguide is a monitor light output waveguide and hasa tapering connecting portion connected to the output sideslab-waveguide.

In this embodiment, the terminal portion of the monitor light signaloutput waveguide connected to the output side slab-waveguide istapering. Thus, the spectrum width is narrow, and a sharp spectrum isobtainable. However, the extent of tapering of the terminal portion islimited.

According to a seventh aspect of the present invention, there isprovided the arrayed waveguide grating according to the second aspect,wherein the second output waveguide is a monitor light output waveguideand has a straight connecting portion with a fixed width directiondimension and connected to the output side slab-waveguide, and the firstoutput waveguides constituting the output waveguides have terminalportions with progressively increasing width direction dimensions as oneapproaches the output side slab-waveguide.

In this embodiment, the monitor light signal output waveguide itself hasa straight terminal portion connected to the output side slab-waveguide,while the first output waveguides each have a flaring terminal portionconnected to the output side slab-waveguide. The terminal portion of themonitor light signal output waveguide connected to the output sideslab-waveguide thus may not be necessarily tapering so long as it ismade thin compared to the terminal portions of the first outputwaveguides.

According to an eighth aspect of the present invention, there isprovided the arrayed waveguide grating according to the second aspect,wherein the waveguides constituting the output waveguides have terminalportions with progressively increasing width direction dimensions as oneapproaches the output side slab-waveguide, the terminal portions of thefirst output waveguides having width direction dimensions increasing atan increased rate.

In this embodiment, it is shown that the monitor light signal outputwaveguide constituting part of the output waveguides has the flaringconnecting portion connected to the output side slab-waveguide. Again inthis case, it is important in view of obtaining a satisfactory spectrumshape that the extent of flaring is less than the terminal portion ofeach first output waveguide.

According to a ninth aspect of the present invention, there is providedan arrayed waveguide grating module comprising: n arrayed waveguidegrating including one or more input waveguides, an input sideslab-waveguide connected to the output side of the input waveguide orwaveguides, a plurality of arrayed waveguides formed on the side of theinput side slab-waveguide opposite the input waveguide or waveguides, anoutput side slab-waveguide connected to the other terminal of thearrayed waveguides, a plurality of first output waveguides connected tothe output side slab-waveguide on the side thereof opposite the arrayedwaveguides and at least one second output waveguide formed together withthe first output waveguides on the side of the output sideslab-waveguide opposite the arrayed waveguides, the afore-saidcomponents being all formed on a substrate and the optical spectrumoutputted from the second output waveguide being different from theoptical spectra outputted from the other output waveguides; and opticalfibers each having one terminal optically connected to at least part ofthe plurality of waveguides constituting the output waveguides of thearrayed waveguide grating.

In this embodiment, this arrayed waveguide grating module is obtained bycombining optical fibers and other components in the arrayed waveguidegrating as set forth in connection with the first aspect of the presentinvention. The other component may be a temperature control circuit forcontrolling the temperature of the arrayed waveguide grating. Thisarrayed waveguide grating module also permits accurate center wavelengthcompensation of each output waveguide of the arrayed waveguide grating.

According to a tenth aspect of the present invention, there is providedan arrayed waveguide grating module comprising: an arrayed waveguidegrating including one or more input waveguides, an input sideslab-waveguide connected to the output side of the input waveguide orwaveguides, a plurality of arrayed waveguides formed on the side of theinput side slab-waveguide opposite the input waveguide or waveguides, anoutput side slab-waveguide connected to the other terminal of thearrayed waveguides, a plurality of first output waveguides connected tothe output side slab-waveguide on the side thereof opposite the arrayedwaveguides and at least one second output waveguide formed together withthe first output waveguides on the side of the output sideslab-waveguide opposite the arrayed waveguides, the afore-saidcomponents being all formed on a substrate and the shape of theconnecting portion of the second output waveguide with respect to theoutput side slab-waveguide being different from the shape of theconnecting portion of the second output waveguides with respect to theoutput side slab-waveguide; and optical fibers each having one terminaloptically connected to at least part of the plurality of waveguidesconstituting the output waveguides of the arrayed waveguide grating.

In this embodiment, this arrayed waveguide grating module is obtained bycombining optical fibers and other components in the arrayed waveguidegrating as set forth in connection with the second aspect of the presentinvention. The other component may be a temperature control circuit forcontrolling the temperature of the arrayed waveguide grating. Thisarrayed waveguide grating module also permits accurate center wavelengthcompensation of each output waveguide of the arrayed waveguide grating.

According to an eleventh aspect of the present invention, there isprovided a wavelength compensation method in an arrayed waveguidegrating module comprising: a monitor light inputting step of inputting amonitor light for check from either one of the input waveguides withrespect to an arrayed waveguide grating module with an arrayed waveguidegrating including one or more input waveguides, an input sideslab-waveguide connected to the output side of the input waveguide orwaveguides, a plurality of arrayed waveguides formed on the side of theinput side slab-waveguide opposite the input waveguide or waveguides, anoutput side slab-waveguide connected to the other terminal of thearrayed waveguides, a plurality of first output waveguides connected tothe output side slab-waveguide on the side thereof opposite the arrayedwaveguides and at least one second output waveguide formed together withthe first output waveguides on the side of the output sideslab-waveguide opposite the arrayed waveguides, the afore-saidcomponents being all formed on a substrate and the optical spectrumoutputted from the second output waveguide being different from theoptical spectra outputted from the other output waveguides; and awavelength compensation step of performing wavelength compensation withrespect to the lights outputted from the first waveguides at the time ofthe light input from the input waveguides by detecting the monitor lightoutputted from the second output waveguide on the basis of the monitorlight inputting step.

In this embodiment, this wavelength compensation method uses the arrayedwaveguide grating module having the arrayed waveguide grating as setforth in connection with the first aspect of the present invention. Thewavelength compensation is performed by inputting the monitor lightsignal for checking from either one of the input waveguides anddetecting the monitor light signal outputted from the second outputwaveguide.

According to a twelfth aspect of the present invention, there isprovided a wavelength compensation method in an arrayed waveguidegrating module comprising: a monitor light inputting step of inputting amonitor light for check from either one of the input waveguides withrespect to an arrayed waveguide grating module with an arrayed waveguidegrating including one or more input waveguides, an input sideslab-waveguide connected to the output side of the input waveguide orwaveguides, a plurality of arrayed waveguides formed on the side of theinput side slab-waveguide opposite the input waveguide or waveguides, anoutput side slab-waveguide connected to the other terminal of thearrayed waveguides, a plurality of first output waveguides connected tothe output side slab-waveguide on the side thereof opposite the arrayedwaveguides and at least one second output waveguide formed together withthe first output waveguides on the side of the output sideslab-waveguide opposite the arrayed waveguides, the afore-saidcomponents being all formed on a substrate and a connecting portion ofthe second output waveguide with respect to the output sideslab-waveguide having a shape different from the shape of connectingportions of the first output waveguides with respect to the output sideslab-waveguide; and a wavelength compensation step of performingwavelength compensation with respect to the lights outputted from thefirst waveguides at the time of the light input from the inputwaveguides by detecting the monitor light outputted from the secondoutput waveguide on the basis of the monitor light inputting step.

In this embodiment, this wavelength compensation method uses the arrayedwaveguide grating module having the arrayed waveguide grating as setforth in connection with the second aspect of the present invention. Thewavelength compensation is performed by inputting the monitor lightsignal for checking from either one of the input waveguides anddetecting the monitor light signal outputted from the second outputwaveguide.

According to a thirteenth aspect of the present invention, there isprovided a wavelength compensation method in an arrayed waveguidegrating module comprising: a monitor light inputting step of inputting amonitor light for check from either one of the input waveguides withrespect to an arrayed waveguide grating module with an arrayed waveguidegrating including one or more input waveguides, an input sideslab-waveguide connected to the output side of the input waveguide orwaveguides, a plurality of arrayed waveguides formed on the side of theinput side slab-waveguide opposite the input waveguide or waveguides, anoutput side slab-waveguide connected to the other terminal of thearrayed waveguides, a plurality of first output waveguides connected tothe output side slab-waveguide on the side thereof opposite the arrayedwaveguides and at least one second output waveguide formed together withthe first output waveguides on the side of the output sideslab-waveguide opposite the arrayed waveguides, the afore-saidcomponents being all formed on a substrate and the second outputwaveguide outputting an optical spectrum different from the opticalspectral outputted from the other output waveguides; an adjusting stepof adjusting the arrayed waveguide grating module such that the secondoutput waveguide outputs a monitor light having a predeterminedwavelength when the monitor light is inputted in the monitor lightinputting step; and a signal processing starting step of starting asignal processing by inputting actually used lights from the inputwaveguides of the arrayed waveguide grating module adjusted in theadjusting step and using wavelength compensated lights outputted fromthe first output waveguides of the arrayed waveguide grating.

In this embodiment, this wavelength compensation method uses the arrayedwaveguide grating module having the arrayed waveguide grating as setforth in connection with the first aspect of the present invention. Thewavelength compensation is performed by inputting the monitor lightsignal for checking from either one of the input waveguides anddetecting the monitor light signal outputted from the second outputwaveguide. Subsequently, a signal processing by inputting the actuallyused light signals from the adjusted arrayed waveguide grating moduleand using the wavelength compensated light signals outputted from thefirst output waveguides of the arrayed waveguide grating.

According to a fourteenth aspect of the present invention, there isprovided a wavelength compensation method in an arrayed waveguidegrating module comprising: a monitor light inputting step of inputting amonitor light for check from either one of the input waveguides withrespect to an arrayed waveguide grating module with an arrayed waveguidegrating including one or more input waveguides, an input sideslab-waveguide connected to the output side of the input waveguide orwaveguides, a plurality of arrayed waveguides formed on the side of theinput side slab-waveguide opposite the input waveguide or waveguides, anoutput side slab-waveguide connected to the other terminal of thearrayed waveguides, a plurality of first output waveguides connected tothe output side slab-waveguide on the side thereof opposite the arrayedwaveguides and at least one second output waveguide formed together withthe first output waveguides on the side of the output sideslab-waveguide opposite the arrayed waveguides, the afore-saidcomponents being all formed on a substrate and a connecting portion ofthe second output waveguide with respect to the output sideslab-waveguide having a shape different from the shape of connectingportions of the first output waveguides with respect to the output sideslab-waveguide; an adjusting step of adjusting the arrayed waveguidegrating module such that the second output waveguide outputs a monitorlight having a predetermined wavelength when the monitor light isinputted in the monitor light inputting step; and a signal processingstarting step of starting a signal processing by inputting actually usedlights from the input waveguides of the arrayed waveguide grating moduleadjusted in the adjusting step and using wavelength compensated lightsoutputted from the first output waveguides of the arrayed waveguidegrating.

In this embodiment, this wavelength compensation method uses the arrayedwaveguide grating module having the arrayed waveguide grating as setforth in connection with the second aspect of the present invention. Thewavelength compensation is performed by inputting the monitor lightsignal for checking from either one of the input waveguides anddetecting the monitor light signal outputted from the second outputwaveguide. Subsequently, a signal processing by inputting the actuallyused light signals from the adjusted arrayed waveguide grating moduleand using the wavelength compensated light signals outputted from thefirst output waveguides of the arrayed waveguide grating.

According to a fifteenth aspect of the present invention, there isprovided a wavelength compensation method in an arrayed waveguidegrating module according to one of claims 3 and 4, wherein in theadjusting step the arrayed waveguide grating module is adjusted bycontrolling the temperature of the arrayed waveguide grating by using atemperature control circuit assembled in the arrayed waveguide gratingmodule such that the second output waveguide outputs a monitor lighthaving a predetermined wavelength.

In this embodiment, in the wavelength compensation method in the arrayedwaveguide grating module as set forth in connection with the thirteenthand fourteenth aspects of the present invention, the temperature of thearrayed waveguide grating is adjusted when matching the wavelength byusing the monitor light signal. The wavelength compensation may also bemade with any other method.

According to a sixteenth aspect of the present invention, there isprovided an optical communication system comprising: an arrayedwaveguide grating module including one or more input waveguides, aninput side slab-waveguide connected to the output side of the inputwaveguide or waveguides, a plurality of arrayed waveguides formed on theside of the input side slab-waveguide opposite the input waveguide orwaveguides, an output side slab-waveguide connected to the otherterminal of the arrayed waveguides, a plurality of first outputwaveguides connected to the output side slab-waveguide on the sidethereof opposite the arrayed waveguides and at least one second outputwaveguide formed together with the first output waveguides on the sideof the output side slab-waveguide opposite the arrayed waveguides, theafore-said components being all formed on a substrate and the opticalspectrum outputted from the second output waveguide being different fromthe optical spectra outputted from the other output waveguides, opticalfibers each having one terminal optically connected to at least part ofthe output side of each of a plurality of waveguides constituting theoutput waveguides of the arrayed waveguide grating, and a temperaturecontrol circuit for controlling at least temperature of the channelwaveguide of the arrayed waveguide grating; a monitor light inputtingmeans, to which a monitor light for check is inputted from either one ofthe input waveguides at the time of checking the arrayed waveguidegrating module; an adjusting step of adjusting the arrayed waveguidegrating module such that the second output waveguide outputs a monitorlight having a predetermined wavelength when the monitor light isinputted in the monitor light inputting means; and a signal processingstarting means of starting a signal processing by inputting actuallyused lights from the input waveguides of the arrayed waveguide gratingmodule adjusted in the adjusting means and using wavelength compensatedlights outputted from the first output waveguides of the arrayedwaveguide grating.

In this embodiment, in this optical communication system, which uses anarrayed waveguide grating module having the arrayed waveguide grating asset forth in connection with the first aspect of the present invention,at the time of checking the arrayed waveguide grating module, thearrayed waveguide grating module is adjusted by inputting a monitorlight signal for checking form either one of the input waveguides suchthat the monitor light signal outputted from the second output waveguidehas a predetermined wavelength. A signal processing using the wavelengthcompensated light signals outputted from the first output waveguides ofthe arrayed waveguide grating, is then started by inputting the actuallyused light signals from the input waveguides of the arrayed waveguidegrating module.

According to a seventeenth aspect of the present invention, there isprovided an optical communication system comprising: an arrayedwaveguide grating module including one or more input waveguides, aninput side slab-waveguide connected to the output side of the inputwaveguide or waveguides, a plurality of arrayed waveguides formed on theside of the input side slab-waveguide opposite the input waveguide orwaveguides, an output side slab-waveguide connected to the otherterminal of the arrayed waveguides, a plurality of first outputwaveguides connected to the output side slab-waveguide on the sidethereof opposite the arrayed waveguides and at least one second outputwaveguide formed together with the first output waveguides on the sideof the output side slab-waveguide opposite the arrayed waveguides, theafore-said components being all formed on a substrate and a connectingportion of the second output waveguide with respect to the output sideslab-waveguide having a shape different from the shape of connectingportions of the first output waveguides with respect to the output sideslab-waveguide, optical fibers each having one terminal opticallyconnected to at least part of the output side of each of a plurality ofwaveguides constituting the output waveguides of the arrayed waveguidegrating, and a temperature control circuit for controlling at leasttemperature of the channel waveguide of the arrayed waveguide grating; amonitor light inputting means, to which a monitor light for check isinputted from either one of the input waveguides at the time of checkingthe arrayed waveguide grating module; an adjusting step of adjusting thearrayed waveguide grating module such that the second output waveguideoutputs a monitor light having a predetermined wavelength when themonitor light is inputted in the monitor light inputting means; and asignal processing starting means of starting a signal processing byinputting actually used lights from the input waveguides of the arrayedwaveguide grating module adjusted in the adjusting means and usingwavelength compensated lights outputted from the first output waveguidesof the arrayed waveguide grating.

In this embodiment, in this optical communication system, which uses anarrayed waveguide grating module having the arrayed waveguide grating asset forth in connection with the first aspect of the present invention,at the time of checking the arrayed waveguide grating module, thearrayed waveguide grating module is adjusted by inputting a monitorlight signal for checking form either one of the input waveguides suchthat the monitor light signal outputted from the monitor light waveguidehas a predetermined wavelength. A signal processing using the wavelengthcompensated light signals outputted from the first output waveguides ofthe arrayed waveguide grating, is then started by inputting the actuallyused light signals from the input waveguides of the arrayed waveguidegrating module.

According to an eighteenth aspect of the present invention, there isprovided an optical communication system comprising: an opticaltransmitting means for transmitting lights having individual wavelengthsas parallel signals; a multiplexer constituted by an arrayed waveguidegrating for multiplexing the optical signals with the individualwavelengths transmitted from the optical transmitting means; a lighttransmitting line, along which the multiplexed light outputted from themultiplexer is transmitted; a node having the array waveguide gratingappropriately arranged in the light transmitting line; a demultiplexerfor demultiplexing the light transmitted from the light transmittingline via the node in order to separate the lights of respectivewavelengths; an optical receiving means for receiving the demultiplexedlight with the individual wavelengths outputted from the demultiplexer;the demultiplexer being an arrayed waveguide grating including one ormore input waveguides, an input side slab-waveguide connected to theoutput side of the input waveguide or waveguides, a plurality of arrayedwaveguides formed on the side of the input side slab-waveguide oppositethe waveguide or waveguides, an output side slab-waveguide connected tothe other terminal of the arrayed waveguides, a plurality of firstoutput waveguides connected to the output side slab-waveguide on theside thereof opposite the arrayed waveguides and at least one secondoutput waveguide formed together with the first output waveguides on theside of the output side slab-waveguide opposite the arrayed waveguides,the afore-said components being all formed on a substrate and the lightinputted to the second output waveguide having a spectrum shapedifferent from the spectrum shape of the lights inputted to the firstoutput waveguides.

In this embodiment, in the optical communication system comprising alight signal transmitting means for transmitting light signals ofdifferent signals, a multiplexer constituted by an arrayed waveguidegrating for multiplexing the light signals of the individual wavelengthsoutputted form the light signal transmitting means, a light signaltransmitting line for transmitting the multiplexed light signaloutputted from the multiplexer, a node disposed on the light signaltransmitting line on an appropriate position thereof and including anarrayed waveguide grating, a demultiplexer constituted by an arrayedwaveguide grating for demultiplexing the inputted light signaltransmitted along the light signal transmitting line and through thenode to separate the light signals of the individual wavelengths, and alight signal receiving means for receiving the separated light signalsof the individual wavelengths from the demultiplexer, the demultiplexeris constituted by the arrayed waveguide grating as set forth inconnection with the first aspect of the present invention.

According to a nineteenth aspect of the present invention, there isprovided an optical communication system comprising: an opticaltransmitting means for transmitting lights having individual wavelengthsas parallel signals; a multiplexer constituted by an arrayed waveguidegrating for multiplexing the optical signals with the individualwavelengths transmitted from the optical transmitting means; a lighttransmitting line, along which the multiplexed light outputted from themultiplexer is transmitted; a node having the array waveguide gratingappropriately arranged in the light transmitting line; a demultiplexerfor demultiplexing the light transmitted from the light transmittingline via the node in order to separate the lights of respectivewavelengths; an optical receiving means for receiving the demultiplexedlight with the individual wavelengths outputted from the demultiplexer;the demultiplexer being an arrayed waveguide grating including one ormore input waveguides, an input side slab-waveguide connected to theoutput side of the input waveguide or waveguides, a plurality of arrayedwaveguides formed on the side of the input side slab-waveguide oppositethe input waveguide or waveguides, an output side slab-waveguideconnected to the other terminal of the arrayed waveguides, a pluralityof first output waveguides connected to the output side slab-waveguideon the side thereof opposite the arrayed waveguides and at least onesecond output waveguide formed together with the first output waveguideson the side of the output side slab-waveguide opposite the arrayedwaveguides, the afore-said components being all formed on a substrateand a connecting portion of the second output waveguide with respect tothe output side slab-waveguide having a shape different from the shapeof connecting portions of the first output waveguides with respect tothe output side slab-waveguide.

In this embodiment, in the optical communication system comprising alight signal transmitting means for transmitting light signals ofdifferent signals, a multiplexer constituted by an arrayed waveguidegrating for multiplexing the light signals of the individual wavelengthsoutputted form the light signal transmitting means, a light signaltransmitting line for transmitting the multiplexed light signaloutputted from the multiplexer, a node disposed on the light signaltransmitting line on an appropriate position thereof and including anarrayed waveguide grating, a demultiplexer constituted by an arrayedwaveguide grating for demultiplexing the inputted light signaltransmitted along the light signal transmitting line and through thenode to separate the light signals of the individual wavelengths, and alight signal receiving means for receiving the separated light signalsof the individual wavelengths from the demultiplexer, the demultiplexeris constituted by the arrayed waveguide grating as set forth inconnection with the second aspect of the present invention.

According to a twentieth aspect of the present invention, there isprovided an optical communication system comprising: a first arrayedwaveguide grating including a transmission line loop having a pluralityof nodes connected one after another in the form of a loop by respectivetransmission lines, the nodes each demultiplexing a multiplexed light toseparate a light having a corresponding wavelength, and a second arrayedwaveguide grating multiplexing the separated lights of the individualwavelengths; the first arrayed waveguide grating being an arrayedwaveguide grating including one or more input waveguides, an input sideslab-waveguide connected to the output side of the input waveguide orwaveguides, a plurality of arrayed waveguides formed on the side of theinput side slab-waveguide opposite the input waveguide or waveguides, anoutput side slab-waveguide connected to the other terminal of thearrayed waveguides, a plurality of first output waveguides connected tothe output side slab-waveguide on the side thereof opposite the arrayedwaveguides and at least one second output waveguide formed together withthe first output waveguides on the side of the output sideslab-waveguide opposite the arrayed waveguides, the afore-saidcomponents being all formed on a substrate and the second outputwaveguide outputting an optical spectrum different from the opticalspectral outputted from the other output waveguides.

In this embodiment, in the optical communication system, which comprisesthe first arrayed waveguide grating including a transmission line loophaving a plurality of nodes connected to one another in a loop fashionby respective transmission lines, a multiplexed light signal beingtransmitted to each of the transmission lines, the nodes eachdemultiplexing the multiplexed light signal to separate the lightsignals of the individual wavelengths, and a second arrayed waveguidegrating for multiplexing the separated light signals of the individualwavelengths, the first arrayed waveguide grating is the arrayedwaveguide grating as set forth in connection with the first aspect ofthe present invention. It is thus possible to obtain wavelengthcompensation using the second output waveguide.

According to a twenty-first aspect of the present invention, there isprovided an optical communication system comprising: a first arrayedwaveguide grating including a transmission line loop having a pluralityof nodes connected one after another in the form of a loop by respectivetransmission lines, the nodes each demultiplexing a multiplexed lightsignal to separate a light signal having a corresponding wavelength, anda second arrayed waveguide grating multiplexing the separated lightsignals of the individual wavelengths; the first arrayed waveguidegrating being an arrayed waveguide grating including one or more inputwaveguides, an input side slab-waveguide connected to the output side ofthe input waveguide or waveguides, a plurality of arrayed waveguidesformed on the side of the input side slab-waveguide opposite thewaveguide or waveguides, an output side slab-waveguide connected to theother terminal of the arrayed waveguides, a plurality of first outputwaveguides connected to the output side slab-waveguide on the sidethereof opposite the arrayed waveguides and at least one second outputwaveguide formed together with the first output waveguides on the sideof the output side slab-waveguide opposite the arrayed waveguides, theafore-said components being all formed on a substrate and a connectingportion of the second output waveguide with respect to the output sideslab-waveguide having a shape different from the shape of connectingportions of the first output waveguides with respect to the output sideslab-waveguide.

In this embodiment, in the optical communication system, which comprisesthe first arrayed waveguide grating including a transmission line loophaving a plurality of nodes connected to one another in a loop fashionby respective transmission lines, a multiplexed light signal beingtransmitted to each of the transmission lines, the nodes eachdemultiplexing the multiplexed light signal to separate the lightsignals of the individual wavelengths, and a second arrayed waveguidegrating for multiplexing the separated light signals of the individualwavelengths, the first arrayed waveguide grating is the arrayedwaveguide grating as set forth in connection with the second aspect ofthe present invention. It is thus possible to obtain wavelengthcompensation using the second output waveguide.

According to a twenty-second aspect of the present invention, there isprovided the optical communication system according to one of theeighteenth to twenty-first, wherein a wavelength meter for wavelengthmonitoring in presetting the wavelength of at least one monitor lightinputted to the at least one input waveguide of the first arrayedwaveguide grating to a predetermined value when the monitor is inputted,is connected to the second output waveguide.

In this embodiment, the exclusive wavelength meter for monitoring themonitor light signal is used.

According to a twenty-third aspect of the present invention, there isprovided the optical communication system according to one of theeighteenth to twenty-first aspects, comprising: a wavelength meter forbeing connected to the second output waveguide when a monitor light isinputted to the at least one input waveguide of the first arrayedwaveguide grating; an adjusting means for adjusting the arrayedwaveguide grating module such that the monitor light measured in thewavelength meter has a predetermined wavelength; and a signal processingstarting means for starting a signal processing by causing the input ofthe actually used lights from the input waveguides of the arrayedwaveguide grating module adjusted by the adjusting means and using thewavelength compensated lights outputted from the output waveguides ofthe arrayed waveguide grating.

In this embodiment, the optical communication system comprises awavelength meter necessary for wavelength compensation for an arrayedwaveguide grating module, an adjusting means for adjusting the arrayedwaveguide, grating module by using the wavelength meter, and a signalprocessing starting means for starting a signal processing using thewavelength compensated light signals.

According to a twenty-fourth aspect of the present invention, there isprovided an optical communication system comprising: an arrayedwaveguide grating including one or more input waveguides, an input sideslab-waveguide connected to the output side of the input waveguide orwaveguides, a plurality of arrayed waveguides formed on the side of theinput side slab-waveguide opposite the input waveguide or waveguides, anoutput side slab-waveguide connected to the other terminal of thearrayed waveguides, a plurality of first output waveguides connected tothe output side slab-waveguide on the side thereof opposite the arrayedwaveguides and at least one second output waveguide formed together withthe first output waveguides on the side of the output sideslab-waveguide opposite the arrayed waveguides, the afore-saidcomponents being all formed on a substrate and the optical spectrumoutputted from the second output waveguide being different from theoptical spectra outputted from the other output waveguides, and opticalfibers each having one terminal optically connected to at least part ofeach of the plurality of waveguides constituting the output waveguidesof the arrayed waveguide grating; and a module compensating meansincluding a Mach zender circuit, in which a free spectral range as ainterval corresponding to one cycle period of loss wavelengthcharacteristic is preset as a desired optical frequency range, and towhich the monitor light outputted from the second output waveguide isinputted when the monitor light is inputted to the at least one inputwaveguide of the first waveguide grating array, a first and a secondphoto-diodes for receiving respective beams branched out from the outputside of the Mach zender circuit, a computing means for taking the ratiobetween the sum of the output currents from the two photo-diodes and theoutput current from either one of the two diodes, a deviation detectingmeans for detecting a wavelength deviation from the computed ratio, anadjusting means for adjusting the arrayed waveguide grating module byusing the detection output from the deviation detecting means such thatthe monitor lights have a predetermined wavelength, and a signalprocessing starting means for starting a signal processing by causinginput of the actually used lights from the input waveguides of thearrayed waveguide grating module adjusted by the adjusting means andusing the wavelength compensated lights outputted from the first outputwaveguides of the arrayed waveguide grating.

In this embodiment, the optical communication device is constituted byusing the first and second photo-diodes in the arrayed waveguide gratingmodule as set forth in connection with ninth aspect of the presentinvention and also using a module compensating means for wavelengthcompensation by using a so-called wavelength detection locker. Thewavelength meter itself is expensive, and the present invention as setforth in connection with the twenty fourth aspect of the presentinvention permits cost reduction of the optical communication deviceitself or an optical communication system using the same opticalcommunication device.

According to a twenty-fifth aspect of the present invention, there isprovided an optical communication system comprising: an arrayedwaveguide grating including one or more input waveguides, an input sideslab-waveguide connected to the output side of the input waveguide orwaveguides, a plurality of arrayed waveguides formed on the side of theinput side slab-waveguide opposite the input waveguide or waveguides, anoutput side slab-waveguide connected to the other terminal of thearrayed waveguides, a plurality of first output waveguides connected tothe output side slab-waveguide on the side thereof opposite the arrayedwaveguides and at least one second output waveguide formed together withthe first output waveguides on the side of the output sideslab-waveguide opposite the arrayed waveguides, the afore-saidcomponents being all formed on a substrate and a connecting portion ofthe second output waveguide with respect to the output sideslab-waveguide having a shape different from the shape of connectingportions of the first output waveguides with respect to the output sideslab-waveguide, and optical fibers each having one terminal opticallyconnected to at least part of each of the plurality of waveguidesconstituting the output waveguides of the arrayed waveguide grating; anda module compensating means including a Mach zender circuit, in which afree spectral range as a interval corresponding to one cycle period ofloss wavelength characteristic is preset as a desired optical frequencyrange, and to which the monitor light outputted from the second outputwaveguide is inputted when the monitor light is inputted to the at leastone input waveguide of the first waveguide grating array, a first and asecond photo-diode for receiving respective beams branched out from theoutput side of the Mach zender circuit, a computing means for taking theratio between the sum of the output currents from the two photo-diodesand the output current from either one of the two diodes, a deviationdetecting means for detecting a wavelength deviation from the computedratio, an adjusting means for adjusting the arrayed waveguide gratingmodule by using the detection output from the deviation detecting meanssuch that the monitor lights have a predetermined wavelength, and asignal processing starting means for starting a signal processing bycausing input of the actually used light signals from the inputwaveguides of the arrayed waveguide grating module adjusted by theadjusting means and using the wavelength compensated lights outputtedfrom the first output waveguides of the arrayed waveguide grating.

In this embodiment, the optical communication device is constituted byusing the first and second photo-diodes in the arrayed waveguide gratingmodule as set forth in connection with tenth aspect of the presentinvention and also using a module compensating means for wavelengthcompensation by using a so-called wavelength detection locker. Thewavelength meter itself is expensive, and the present invention as setforth in connection with the twenty fifth aspect of the presentinvention permits cost reduction of the optical communication deviceitself or an optical communication system using the same opticalcommunication device.

According to a twenty-sixth aspect of the present invention, there isprovided an arrayed waveguide grating comprising: at least one inputwaveguides; an input side slab-waveguide with the input side thereofconnected to the output side of the input waveguide or waveguides; achannel waveguide array including a plurality of waveguides with lengthsprogressively increasing by a predetermined waveguide length difference,the input side of the waveguides being connected to the output side ofthe input side slab-waveguide; an output side slab-waveguide with theinput side thereof connected to the output side of the plurality ofwaveguides constituting the channel waveguide array; and a plurality ofwaveguides as output waveguides each having one terminal connected tothe output side of the output side slab-waveguide, the optical spectrumof the light outputted from a second waveguide as one of the outputwaveguides being different from the optical spectrum of the lightsoutputted from first waveguides as the remaining output waveguides.

In this embodiment, a light signal spectrum different from the lightsignal spectrum outputted from the first waveguides, among the outputwaveguides connected to the output side slab-waveguide provided in theoutput side of the arrayed waveguide grating, is obtained from thesecond waveguide, and it is used for center wavelength compensation ofeach waveguide of the arrayed waveguide grating.

According to a twenty-seventh aspect of the present invention, there isprovided an arrayed waveguide grating comprising: at least one inputwaveguides; an input side slab-waveguide with the input side thereofconnected to the output side of the input waveguide or waveguides; achannel waveguide array including a plurality of waveguides with lengthsprogressively increasing by a predetermined waveguide length difference,the input side of the waveguides being connected to the output side ofthe input side slab-waveguide; an output side slab-waveguide with theinput side thereof connected to the output side of the plurality ofwaveguides constituting the channel waveguide array; and a plurality ofwaveguides as output waveguides each having one terminal connected tothe output side of the output side slab-waveguide, a connecting portionof the second output waveguide with respect to the output sideslab-waveguide having a shape different from the shape of connectingportions of the first output waveguides with respect to the output sideslab-waveguide.

In this embodiment, a light signal spectrum different from the lightsignal spectrum outputted from the first waveguides, among the outputwaveguides connected to the output side slab-waveguide provided in theoutput side of the arrayed waveguide grating, is obtained from thesecond waveguide, and it is used for center wavelength compensation ofeach waveguide of the arrayed waveguide grating.

According to a twenty-eighth aspect of the present invention, there isprovided the arrayed waveguide grating according to one of thetwenty-sixth to twenty-seventh aspects, wherein the second outputwaveguide constituting the output waveguides is a monitor lightwaveguide for wavelength monitoring.

In this embodiment, the second output waveguide is used for thewavelength monitoring.

According to a twenty-ninth aspect of the present invention, there isprovided the arrayed waveguide grating according to the twenty-sixthaspect, wherein the second output waveguide constituting the outputwaveguides outputs an output spectrum having a narrower spectral widththan the spectral width of the output optical spectra of the firstoutput waveguides.

In this embodiment, the spectrum width of the spectrum of the lightsignal outputted from the second output waveguide is narrow compared tothe usual waveguides as output waveguides. It is thus possible toreadily specify the center wavelength, and the range in which errorsoccur is small.

According to a thirtieth aspect of the present invention, there isprovided the arrayed waveguide grating according to the twenty-sixthaspect, wherein the second output waveguide constituting the outputwaveguides outputs an optical spectrum having a sharper peak than thepeak of the optical spectra of the first output waveguides.

In this embodiment, the spectrum of the light signal outputted from thesecond output waveguide has a sharp peak compared to the usualwaveguides as the output waveguides.

According to a thirty-first aspect of the present invention, there isprovided the arrayed waveguide grating according to the twenty-seventhaspect, wherein the second output waveguide is a monitor light outputwaveguide and has a tapering connecting portion connected to the outputside slab-waveguide.

In this embodiment, the terminal portion of the monitor light signaloutput waveguide connected to the output side slab-waveguide istapering. Thus, the spectrum width is narrow, and a sharp spectrum isobtainable. However, the extent of tapering of the terminal portion islimited.

According to a thirty-second aspect of the present invention, there isprovided the arrayed waveguide grating according to the twenty-seventhaspect, wherein the second output waveguide is a monitor light outputwaveguide and has a straight connecting portion with a fixed widthdirection dimension and connected to the output side slab-waveguide, andthe first output waveguides constituting the output waveguides haveterminal portions with progressively increasing width directiondimensions as one approaches the output side slab-waveguide.

In this embodiment, the monitor light signal output waveguide itself hasa straight terminal portion connected to the output side slab-waveguide,while the first output waveguides each have a flaring terminal portionconnected to the output side slab-waveguide. The terminal portion of themonitor light signal output waveguide connected to the output sideslab-waveguide thus may not be necessarily tapering so long as it ismade thin compared to the terminal portions of the first outputwaveguides.

According to a thirty-third aspect of the present invention, there isprovided the arrayed waveguide grating according to the twenty-seventhaspect, wherein the waveguides constituting the output waveguides haveterminal portions with progressively increasing width directiondimensions as one approaches the output side slab-waveguide, theterminal portions of the first output waveguides having width directiondimensions increasing at an increased rate.

In this embodiment, it is shown that the monitor light signal outputwaveguide constituting part of the output waveguides has the flaringconnecting portion connected to the output side slab-waveguide. Again inthis case, it is important in view of obtaining a satisfactory spectrumshape that the extent of flaring is less than the terminal portion ofeach first output waveguide.

According to a thirty-fourth aspect of the present invention, there isprovided an arrayed waveguide grating module comprising: an arrayedwaveguide grating including at least one input waveguides, an input sideslab-waveguide with the input side thereof connected to the output sideof the input waveguide or waveguides, a channel waveguide arrayincluding a plurality of waveguides with lengths progressivelyincreasing by a predetermined waveguide length difference, the inputside of the waveguides being connected to the output side of the inputside slab-waveguide, an output side slab-waveguide with the input sidethereof connected to the output side of the plurality of waveguidesconstituting the channel waveguide array and a plurality of outputwaveguides each having one terminal connected to the output side of theoutput side slab-waveguide, the optical spectrum of the light outputtedfrom a second waveguide as one of the output waveguides being differentfrom the optical spectrum of the lights outputted from first waveguidesas the remaining output waveguides; and optical fibers each having oneterminal optically connected to at least part of the plurality ofwaveguides constituting the output waveguides of the arrayed waveguidegrating.

In this embodiment, this arrayed waveguide grating module is obtained bycombining optical fibers and other components in the arrayed waveguidegrating as set forth in connection with the twenty-sixth aspect of thepresent invention. The other component may be a temperature controlcircuit for controlling the temperature of the arrayed waveguidegrating. This arrayed waveguide grating module also permits accuratecenter wavelength compensation of each output waveguide of the arrayedwaveguide grating.

According to a thirty-fifth aspect of the present invention, there isprovided an arrayed waveguide grating module comprising: an arrayedwaveguide grating including at least one input waveguides, an input sideslab-waveguide with the input side thereof connected to the output sideof the input waveguide or waveguides, a channel waveguide arrayincluding a plurality of waveguides with lengths progressivelyincreasing by a predetermined waveguide length difference, the inputside of the waveguides being connected to the output side of the inputside slab-waveguide, an output side slab-waveguide with the input sidethereof connected to the output side of the plurality of waveguidesconstituting the channel waveguide array and a plurality of outputwaveguides each having one terminal; connected to the output side of theoutput side slab-waveguide, a connecting portion of the second outputwaveguide with respect to the output side slab-waveguide having a shapedifferent from the shape of connecting portions of the first outputwaveguides with respect to the output side slab-waveguide; and opticalfibers each having one terminal optically connected to at least part ofthe plurality of waveguides constituting the output waveguides of thearrayed waveguide grating.

In this embodiment, this arrayed waveguide grating module is obtained bycombining optical fibers and other components in the arrayed waveguidegrating as set forth in connection with the twenty-seventh aspect of thepresent invention. The other component may be a temperature controlcircuit for controlling the temperature of the arrayed waveguidegrating. This arrayed waveguide grating module also permits accuratecenter wavelength compensation of each output waveguide of the arrayedwaveguide grating.

According to a thirty-sixth aspect of the present invention, there isprovided a wavelength compensation method in an arrayed grating modulehaving an arrayed waveguide grating which includes one or more inputwaveguides, an input side slab-waveguide with the input side thereofconnected to the output side of the input waveguide or waveguides, achannel waveguide array including a plurality of waveguides with lengthsprogressively increasing by a predetermined waveguide length difference,the input side of the waveguides being connected to the output side ofthe input side slab-waveguide, an output side slab-waveguide with theinput side thereof connected to the output side of the plurality ofwaveguides constituting the channel waveguide array and a plurality ofoutput waveguides each having one terminal connected to the output sideof the output side slab-waveguide, the optical spectrum of the lightfrom a second waveguide, i.e., a monitor light waveguide, as one of theoutput waveguides connected to the input side of the output sideslab-waveguide being different from the optical spectrum of the lightsfrom first waveguides as the remaining output waveguides, the wavelengthcompensation method comprising a monitor light inputting step ofinputting a monitor light for checking from either one of the inputwaveguides; and a wavelength compensation step of performing wavelengthcompensation with respect to the lights outputted from the firstwaveguides at the time of the light input from the input waveguides bydetecting the monitor light outputted from the monitor waveguide on thebasis of the monitor light inputting step.

In this embodiment, this wavelength compensation method uses the arrayedwaveguide grating module having the arrayed waveguide grating as setforth in connection with the twenty-sixth aspect of the presentinvention. The wavelength compensation is performed by inputting themonitor light signal for checking from either one of the inputwaveguides and detecting the monitor light signal outputted from thesecond output waveguide.

According to a thirty-seventh aspect of the present invention, there isprovided a wavelength compensation method in an arrayed grating modulehaving an arrayed waveguide grating which includes one or more inputwaveguides, an input side slab-waveguide with the input side thereofconnected to the output side of the input waveguide or waveguides, achannel waveguide array including a plurality of waveguides with lengthsprogressively increasing by a predetermined waveguide length difference,the input side of the waveguides being connected to the output side ofthe input side slab-waveguide, an output side slab-waveguide with theinput side thereof connected to the output side of the plurality ofwaveguides constituting the channel waveguide array and a plurality ofoutput waveguides each having one terminal connected to the output sideof the output side slab-waveguide, a connecting portion of the secondoutput waveguide, i.e., a monitor light waveguide, with respect to theoutput side slab-waveguide having a shape different from the shape ofconnecting portions of the first output waveguides with respect to theoutput side slab-waveguide; the wavelength compensation methodcomprising a monitor light inputting step of inputting a monitor lightfor checking from either one of the input waveguides; and a wavelengthcompensation step of performing wavelength compensation with respect tothe lights outputted from the first waveguides at the time of the lightinput from the input waveguides by detecting the monitor light outputtedfrom the monitor output waveguide on the basis of the monitor lightinputting step.

In this embodiment, this wavelength compensation method uses the arrayedwaveguide grating module having the arrayed waveguide grating as setforth in connection with the twenty-seventh aspect of the presentinvention. The wavelength compensation is performed by inputting themonitor light signal for checking from either one of the inputwaveguides and detecting the monitor light signal outputted from thesecond output waveguide.

According to a thirty-eighth aspect of the present invention, there isprovided a wavelength compensation method in an arrayed grating modulehaving an arrayed waveguide grating which includes one or more inputwaveguides, an input side slab-waveguide with the input side thereofconnected to the output side of the input waveguide or waveguides, achannel waveguide array including a plurality of waveguides with lengthsprogressively increasing by a predetermined waveguide length difference,the input side of the waveguides being connected to the output side ofthe input side slab-waveguide, an output side slab-waveguide with theinput side thereof connected to the output side of the plurality ofwaveguides constituting the channel waveguide array and a plurality ofoutput waveguides each having one terminal connected to the output sideof the output side slab-waveguide, the optical spectrum of the lightfrom a second waveguide, i.e., a monitor light waveguide, as one of theoutput waveguides connected to the input side of the output sideslab-waveguide being different from the optical spectrum of the lightsfrom first waveguides as the remaining output waveguides; the wavelengthcompensation method comprising: a monitor light inputting step ofinputting a monitor light for checking from either one of the inputwaveguides; an adjusting step of adjusting the arrayed waveguide gratingmodule such that the monitor light waveguide outputs a monitor lighthaving a predetermined wavelength when the monitor light is inputted inthe monitor light inputting step; and a wavelength compensation step ofperforming wavelength compensation with respect to the lights outputtedfrom the first waveguides at the time of the light input from the inputwaveguides by detecting the monitor light outputted from the monitoroutput waveguide on the basis of the monitor light inputting step.

In this embodiment, this wavelength compensation method uses the arrayedwaveguide grating module having the arrayed waveguide grating as setforth in connection with the twenty-sixth aspect of the presentinvention. The wavelength compensation is performed by inputting themonitor light signal for checking from either one of the inputwaveguides and detecting the monitor light signal outputted from thesecond output waveguide. Subsequently, a signal processing by inputtingthe actually used light signals from the adjusted arrayed waveguidegrating module and using the wavelength compensated light signalsoutputted from the first output waveguides of the arrayed waveguidegrating.

According to a thirty-ninth aspect of the present invention, there isprovided a wavelength compensation method in an arrayed grating modulehaving an arrayed waveguide grating which includes one or more inputwaveguides, an input side slab-waveguide with the input side thereofconnected to the output side of the input waveguide or waveguides, achannel waveguide array including a plurality of waveguides with lengthsprogressively increasing by a predetermined waveguide length difference,the input side of the waveguides being connected to the output side ofthe input side slab-waveguide, an output side slab-waveguide with theinput side thereof connected to the output side of the plurality ofwaveguides constituting the channel waveguide array and a plurality ofoutput waveguides each having one terminal connected to the output sideof the output side slab-waveguide, a connecting portion of the secondoutput waveguide, i.e., a monitor light waveguide, with respect to theoutput side slab-waveguide having a shape different from the shape ofconnecting portions of the first output waveguides with respect to theoutput side slab-waveguide; the wavelength compensation methodcomprising: a monitor light inputting step of inputting a monitor lightfor checking from either one of the input waveguides; an adjusting stepof adjusting the arrayed waveguide grating module such that the monitorlight waveguide outputs a monitor light having a predeterminedwavelength when the monitor light is inputted in the monitor lightinputting step; and a wavelength compensation step of performingwavelength compensation with respect to the lights outputted from thefirst waveguides at the time of the light input from the inputwaveguides by detecting the monitor light outputted from the monitoroutput waveguide on the basis of the monitor light inputting step.

In this embodiment, this wavelength compensation method uses the arrayedwaveguide grating module having the arrayed waveguide grating as setforth in connection with the twenty-seventh aspect of the presentinvention. The wavelength compensation is performed by inputting themonitor light signal for checking from either one of the inputwaveguides and detecting the monitor light signal outputted from thesecond output waveguide. Subsequently, a signal processing by inputtingthe actually used light signals from the adjusted arrayed waveguidegrating module and using the wavelength compensated light signalsoutputted from the first output waveguides of the arrayed waveguidegrating.

According to a fortieth aspect of the present invention, there isprovided the wavelength compensation method in an arrayed waveguidegrating module according to one of the thirteenth to thirty-ninthaspects, wherein in the adjusting step the arrayed waveguide gratingmodule is adjusted by using a temperature control circuit assembled inthe arrayed waveguide grating module such that the monitor lightwaveguide outputs a monitor light having a predetermined wavelength.

In this embodiment, in the wavelength compensation method in the arrayedwaveguide grating module as set forth in connection with thethirty-eighth and thirty-ninth aspects of the present invention, thetemperature of the arrayed waveguide grating is adjusted when matchingthe wavelength by using the monitor light signal. The wavelengthcompensation may also be made with any other method.

According to a forty-first aspect of the present invention, there isprovided an optical communication system comprising: an arrayedwaveguide grating module including at least one input waveguides, aninput side slab-waveguide with the input side thereof connected to theoutput side of the input waveguide or waveguides, a channel waveguidearray including a plurality of waveguides with lengths progressivelyincreasing by a predetermined waveguide length difference, the inputside of the waveguides being connected to the output side of the inputside slab-waveguide, an output side slab-waveguide with the input sidethereof connected to the output side of the plurality of waveguidesconstituting the channel waveguide array and a plurality of outputwaveguides each having one terminal; connected to the output side of theoutput side slab-waveguide, the optical spectrum of the light outputtedfrom a second waveguide, i.e., a monitor light waveguide, as one of theoutput waveguides being different from the optical spectrum of thelights outputted from the remaining output waveguides, optical fiberseach having one terminal optically connected to at least part of theplurality of waveguides constituting the output waveguides of thearrayed waveguide grating, and a temperature control circuit foradjusting at least the temperature of the channel waveguide array of thearrayed waveguide grating; a monitor light inputting means for inputtinga monitor light for checking from either one of the input waveguides atthe time of the arrayed waveguide grating check; an adjusting means ofadjusting the arrayed waveguide grating module such that the monitorwaveguide outputs a monitor light having a predetermined wavelength whenthe monitor light is inputted in the monitor light inputting step; and asignal processing starting means of starting a signal processing byinputting actually used lights from the input waveguides of the arrayedwaveguide grating module adjusted in the adjusting means and usingwavelength compensated lights outputted from the first output waveguidesof the arrayed waveguide grating.

In this embodiment, in this optical communication system, which uses anarrayed waveguide grating module having the arrayed waveguide grating asset forth in connection with the twenty-sixth aspect of the presentinvention, at the time of checking the arrayed waveguide grating module,the arrayed waveguide grating module is adjusted by inputting a monitorlight signal for checking form either one of the input waveguides suchthat the monitor light signal outputted from the second output waveguidehas a predetermined wavelength. A signal processing using the wavelengthcompensated light signals outputted from the first output waveguides ofthe arrayed waveguide grating, is then started by inputting the actuallyused light signals from the input waveguides of the arrayed waveguidegrating module.

According to a forty-second aspect of the present invention, there isprovided an optical communication system comprising: an arrayedwaveguide grating module including at least one input waveguides, aninput side slab-waveguide with the input side thereof connected to theoutput side of the input waveguide or waveguides, a channel waveguidearray including a plurality of waveguides with lengths progressivelyincreasing by a predetermined waveguide length difference, the inputside of the waveguides being connected to the output side of the inputside slab-waveguide, an output side slab-waveguide with the input sidethereof connected to the output side of the plurality of waveguidesconstituting the channel waveguide array and a plurality of outputwaveguides each having one terminal connected to the output side of theoutput side slab-waveguide, a connecting portion of the monitorwaveguide as the second output waveguide with respect to the output sideslab-waveguide having a shape different from the shape of connectingportions of the first output waveguides with respect to the output sideslab-waveguide, optical fibers each having one terminal opticallyconnected to at least part of the plurality of waveguides constitutingthe output waveguides of the arrayed waveguide grating, and atemperature control circuit for adjusting at least the temperature ofthe channel waveguide array of the arrayed waveguide grating; a monitorlight inputting means for inputting a monitor light for checking fromeither one of the input waveguides at the time of the arrayed waveguidegrating check; an adjusting means of adjusting the arrayed waveguidegrating module such that the monitor waveguide outputs a monitor lighthaving a predetermined wavelength when the monitor light is inputted inthe monitor light inputting step; and a signal processing starting meansof starting a signal processing by inputting actually used lights fromthe input waveguides of the arrayed waveguide grating module adjusted inthe adjusting means and using wavelength compensated lights outputtedfrom the first output waveguides of the arrayed waveguide grating.

In this embodiment, in this optical communication system, which uses anarrayed waveguide grating module having the arrayed waveguide grating asset forth in connection with the twenty-seventh aspect of the presentinvention, at the time of checking the arrayed waveguide grating module,the arrayed waveguide grating module is adjusted by inputting a monitorlight signal for checking form either one of the input waveguides suchthat the monitor light signal outputted from the second output waveguidehas a predetermined wavelength. A signal processing using the wavelengthcompensated light signals outputted from the first output waveguides ofthe arrayed waveguide grating, is then started by inputting the actuallyused light signals from the input waveguides of the arrayed waveguidegrating module.

According to a forty-third aspect of the present invention, there isprovided an optical communication system comprising: an opticaltransmitting means for transmitting light signals having individualwavelengths as parallel signals; a multiplexer constituted by an arrayedwaveguide grating for multiplexing the optical signals with theindividual wavelengths transmitted from the optical transmitting means;a light transmitting line, along which the multiplexed light outputtedfrom the multiplexer is transmitted; a node having the array waveguidegrating appropriately arranged in the light transmitting line; ademultiplexer for demultiplexing the light transmitted from the lighttransmitting line via the node in order to separate the lights ofrespective wavelengths; an optical receiving means for receiving thedemultiplexed light signal with the individual wavelengths outputtedfrom the demultiplexer; the demultiplexer being an arrayed waveguidegrating including one or more input waveguides, an input sideslab-waveguide connected to the output side of the input waveguide orwaveguides, a channel waveguide array including a plurality ofwaveguides with lengths progressively increasing by a predeterminedwaveguide length difference, the input side of the waveguides beingconnected to the output side of the input side slab-waveguide, an outputside slab-waveguide with the input side thereof connected to the outputside of the plurality of waveguides constituting the channel waveguidearray, and a plurality of waveguides as output waveguides each havingone terminal connected to the output side of the output sideslab-waveguide, the optical spectrum of the light outputted from asecond waveguide as one of the output waveguides being different fromthe optical spectrum of the lights outputted from first waveguides asthe remaining output waveguides.

In this embodiment, in the optical communication system comprising alight signal transmitting means for transmitting light signals ofdifferent signals, a multiplexer constituted by an arrayed waveguidegrating for multiplexing the light signals of the individual wavelengthsoutputted form the light signal transmitting means, a light signaltransmitting line for transmitting the multiplexed light signaloutputted from the multiplexer, a node disposed on the light signaltransmitting line on an appropriate position thereof and including anarrayed waveguide grating, a demultiplexer constituted by an arrayedwaveguide grating for demultiplexing the inputted light signaltransmitted along the light signal transmitting line and through thenode to separate the light signals of the individual wavelengths, and alight signal receiving means for receiving the separated light signalsof the individual wavelengths from the demultiplexer, the demultiplexeris constituted by the arrayed waveguide grating as set forth inconnection with the twenty-sixth aspect of the present invention.

According to a forty-fourth aspect of the present invention, there isprovided an optical communication system comprising: an opticaltransmitting means for transmitting light signals having individualwavelengths as parallel signals; a multiplexer constituted by an arrayedwaveguide grating for multiplexing the optical lights with theindividual wavelengths transmitted from the optical transmitting means;a light transmitting line, along which the multiplexed light outputtedfrom the multiplexer is transmitted; a node having the array waveguidegrating appropriately arranged in the light transmitting line; ademultiplexer for demultiplexing the light transmitted from the lighttransmitting line via the node in order to separate the lights ofrespective wavelengths; an optical receiving means for receiving thedemultiplexed light with the individual wavelengths outputted from thedemultiplexer; the demultiplexer being an arrayed waveguide gratingincluding one or more input waveguides, an input side slab-waveguideconnected to the output side of the input waveguide or waveguides, achannel waveguide array including a plurality of waveguides with lengthsprogressively increasing by a predetermined waveguide length difference,the input side of the waveguides being connected to the output side ofthe input side slab-waveguide, an output side slab-waveguide with theinput side thereof connected to the output side of the plurality ofwaveguides constituting the channel waveguide array, and a plurality ofwaveguides as output waveguides each having one terminal connected tothe output side of the output side slab-waveguide, a connecting portionof the second output waveguide with respect to the output sideslab-waveguide having a shape different from the shape of connectingportions of the first output waveguides with respect to the output sideslab-waveguide.

In this embodiment, in the optical communication system comprising alight signal transmitting means for transmitting light signals ofdifferent signals, a multiplexer constituted by an arrayed waveguidegrating for multiplexing the light signals of the individual wavelengthsoutputted form the light signal transmitting means, a light signaltransmitting line for transmitting the multiplexed light signaloutputted from the multiplexer, a node disposed on the light signaltransmitting line on an appropriate position thereof and including anarrayed waveguide grating, a demultiplexer constituted by an arrayedwaveguide grating for demultiplexing the inputted light signaltransmitted along the light signal transmitting line and through thenode to separate the light signals of the individual wavelengths, and alight signal receiving means for receiving the separated light signalsof the individual wavelengths from the demultiplexer, the demultiplexeris constituted by the arrayed waveguide grating as set forth inconnection with the twenty-seventh aspect of the present invention.

According to a forty-fifth aspect of the present invention, there isprovided an optical communication system comprising: a first arrayedwaveguide grating including a transmission line loop having a pluralityof nodes connected one after another in the form of a loop by respectivetransmission lines, the nodes each demultiplexing a multiplexed light toseparate a light having a corresponding wavelength, and a second arrayedwaveguide grating multiplexing the separated lights of the individualwavelengths; the first arrayed waveguide grating being an elementincluding one or more input waveguides, an input side slab-waveguideconnected to the output side of the input waveguide or waveguides, achannel waveguide array including a plurality of waveguides with lengthsprogressively increasing by a predetermined waveguide length difference,the input side of the waveguides being connected to the output side ofthe input side slab-waveguide, an output side slab-waveguide with theinput side thereof connected to the output side of the plurality ofwaveguides constituting the channel waveguide array, and a plurality ofwaveguides as output waveguides each having one terminal connected tothe output side of the output side slab-waveguide, the optical spectrumof the light outputted from a second waveguide as one of the outputwaveguides being different from the optical spectrum of the lightsoutputted from first waveguides as the remaining output waveguides.

In this embodiment, in the optical communication system, which comprisesa first arrayed waveguide grating including a transmission line loophaving a plurality of nodes connected to one another in a loop fashionby respective transmission lines, a multiplexed light signal beingtransmitted to these transmission lines, the nodes each demultiplexingthe multiplexed light signal to separate the light signals of theindividual wavelengths, and a second arrayed waveguide grating formultiplexing the separated light signals of the individual wavelengths,the first arrayed waveguide grating is the arrayed waveguide grating asset forth in connection with the twenty-sixth aspect of the presentinvention.

According to a forty-sixth aspect of the present invention, there isprovided an optical communication system comprising: a first arrayedwaveguide grating including a transmission line loop having a pluralityof nodes connected one after another in the form of a loop by respectivetransmission lines, the nodes each demultiplexing a multiplexed lightsignal to separate a light signal having a corresponding wavelength, anda second arrayed waveguide grating multiplexing the separated lightsignals of the individual wavelengths; he first arrayed waveguidegrating being an element including one or more input waveguides, aninput side slab-waveguide connected to the output side of the inputwaveguide or waveguides, a channel waveguide array including a pluralityof waveguides with lengths progressively increasing by a predeterminedwaveguide length difference, the input side of the waveguides beingconnected to the output side of the input side slab-waveguide, an outputside slab-waveguide with the input side thereof connected to the outputside of the plurality of waveguides constituting the channel waveguidearray, and a plurality of waveguides as output waveguides each havingone terminal connected to the output side of the output sideslab-waveguide, a connecting portion of the second output waveguide withrespect to the output side slab-waveguide having a shape different fromthe shape of connecting portions of the first output waveguides withrespect to the output side slab-waveguide.

In this embodiment, in the optical communication system, which comprisesa first arrayed waveguide grating including a transmission line loophaving a plurality of nodes connected to one another in a loop fashionby respective transmission lines, a multiplexed light signal beingtransmitted to these transmission lines, the nodes each demultiplexingthe multiplexed light signal to separate the light signals of theindividual wavelengths, and a second arrayed waveguide grating formultiplexing the separated light signals of the individual wavelengths,the first arrayed waveguide grating is the arrayed waveguide grating asset forth in connection with the twenty-seventh aspect of the presentinvention.

According to the forty-seventh aspect of the present invention, there isprovided the optical communication system according to one of theforty-third to forty-sixth aspects, wherein a wavelength meter forwavelength monitoring in presetting the wavelength of at least onemonitor light inputted to the at least one input waveguide of the firstarrayed waveguide grating to a predetermined value when the monitor isinputted, is connected to the second output waveguide.

In this embodiment, the exclusive wavelength meter for monitoring themonitor light signal is used.

According to a forty-eighth aspect of the present invention, there isprovided the optical communication system according to one of theforty-third to forty-sixth aspects, comprising: a wavelength meter forbeing connected to the second output waveguide when a monitor light isinputted to the at least one input waveguide of the first arrayedwaveguide grating; an adjusting means for adjusting the arrayedwaveguide grating module such that the monitor light measured in thewavelength meter has a predetermined wavelength; and a signal processingstarting means for starting a signal processing by causing the input ofthe actually used light signals from the input waveguides of the arrayedwaveguide grating module adjusted by the adjusting means and using thewavelength compensated lights outputted from the output waveguides ofthe arrayed waveguide grating.

In this embodiment, the optical communication system comprises awavelength meter necessary for wavelength compensation for an arrayedwaveguide grating module, an adjusting means for adjusting the arrayedwaveguide grating module by using the wavelength meter, and a signalprocessing starting means for starting a signal processing using thewavelength compensated light signals.

According to a forty-ninth aspect of the present invention, there isprovided an optical communication system comprising; an arrayedwaveguide grating module including at least one input waveguides, aninput side slab-waveguide with the input side thereof connected to theoutput side of the input waveguide or waveguides, a channel waveguidearray including a plurality of waveguides with lengths progressivelyincreasing by a predetermined waveguide length difference, the inputside of the waveguides being connected to the output side of the inputside slab-waveguide, an output side slab-waveguide with the input sidethereof connected to the output side of the plurality of waveguidesconstituting the channel waveguide array and a plurality of outputwaveguides each having one terminal connected to the output side of theoutput side slab-waveguide, the optical spectrum of the light outputtedfrom a second waveguide as one of the output waveguides being differentfrom the optical spectrum of the lights outputted from first waveguidesas the remaining output waveguides, and optical fibers each having oneterminal optically connected to at least part of the plurality ofwaveguides constituting the output waveguides of the arrayed waveguidegrating; and a module compensating means including a Mach zendercircuit, in which a free spectral range as a interval corresponding toone cycle period of loss wavelength characteristic is preset as adesired optical frequency range, and to which the monitor lightoutputted from the second output waveguide is inputted when the monitorlight is inputted to the at least one input waveguide of the firstwaveguide grating array, a first and a second photo-diodes for receivingrespective beams branched out from the output side of the Mach zendercircuit, a computing means for taking the ratio between the sum of theoutput currents from the two photo-diodes and the output current fromeither one of the two diodes, a deviation detecting means for detectinga wavelength deviation from the computed ratio, an adjusting means foradjusting the arrayed waveguide grating module by using the detectionoutput from the deviation detecting means such that the monitor lightshave a predetermined wavelength, and a signal processing starting meansfor starting a signal processing by causing input of the actually usedlight signals from the input waveguides of the arrayed waveguide gratingmodule adjusted by the adjusting means and using the wavelengthcompensated lights outputted from the first output waveguides of thearrayed waveguide grating.

In this embodiment, the optical communication device is constructed byusing the first and second photo-diodes in the arrayed waveguide gratingmodule as set forth in connection with the thirty fourth aspect of thepresent invention and adding the module compensating means forwavelength compensation using the so-called wavelength detecting locker.The wavelength meter itself is expensive, and the fiftieth aspect of thepresent invention permits cost reduction of the optical communicationdevice itself or the entire optical communication system using theoptical communication device.

According to a fiftieth aspect of the present invention, there isprovided an optical communication system comprising: an arrayedwaveguide grating module having an arrayed waveguide grating includingone or more input waveguides, an input side slab-waveguide with theinput side thereof connected to the output side of the input waveguideor waveguides, a channel waveguide array including a plurality ofwaveguides with lengths progressively increasing by a predeterminedwaveguide length difference, the input side of the waveguides beingconnected to the output side of the input side slab-waveguide, an outputside slab-waveguide with the input side thereof connected to the outputside of the plurality of waveguides constituting the channel waveguidearray and a plurality of output waveguides each having one terminalconnected to the output side of the output side slab-waveguide, aconnecting portion of the second output waveguide with respect to theoutput side slab-waveguide having a shape different from the shape ofconnecting portions of the first output waveguides with respect to theoutput side slab-waveguide, and optical fibers each having one terminaloptically connected to at least part of the plurality of waveguidesconstituting the output waveguides of the arrayed waveguide grating; amodule compensating means including a Mach zender circuit, in which afree spectral range as a interval corresponding to one cycle period ofloss wavelength characteristic is preset as a desired optical frequencyrange, and to which the monitor light outputted from the second outputwaveguide is inputted when the monitor light is inputted to the at leastone input waveguide of the first waveguide grating array, a first and asecond photo-diodes for receiving respective beams branched out from theoutput side of the Mach zender circuit, a computing means for taking theratio between the sum of the output currents from the two photo-diodesand the output current from either one of the two diodes, a deviationdetecting means for detecting a wavelength deviation from the computedratio, an adjusting means for adjusting the arrayed waveguide gratingmodule by using the detection output from the deviation detecting meanssuch that the monitor lights have a predetermined wavelength, and asignal processing starting means for starting a signal processing bycausing input of the actually used lights from the input waveguides ofthe arrayed waveguide grating module adjusted by the adjusting means andusing the wavelength compensated lights outputted from the first outputwaveguides of the arrayed waveguide grating.

In this embodiment, the optical communication device is constructed byusing the first and second photo-diodes in the arrayed waveguide gratingmodule as set forth in connection with the thirty-fifth aspect of thepresent invention and adding the module compensating means forwavelength compensation using the so-called wavelength detecting locker.The wavelength meter itself is expensive, and the fiftieth aspect of thepresent invention permits cost reduction of the optical communicationdevice itself or the entire optical communication system using theoptical communication device.

Other objects and features will be clarified from the followingdescription with reference to attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing an arrayed wavelength grating as a firstembodiment of the present invention;

FIG. 2 is, to an enlarged scale, a plan view showing the neighborhood ofthe output terminal of the output side slab-waveguide in the arrayedwaveguide grating of first embodiment;

FIGS. 3(a) and 3(b) are drawings showing a first shape of the connectionportion of the output waveguide and the optical spectral shape from thearrayed waveguide grating;

FIGS. 4(a) and 4(b) are drawings showing a second shape of theconnection portion of the output waveguide and the optical spectralshape from the arrayed waveguide grating;

FIGS. 5(a) and 5(b) are drawings showing a third shape of the connectionportion of the output waveguide and the optical spectral shape from thearrayed waveguide grating;

FIGS. 6(a) and 6(b) are drawings showing a fourth shape of theconnection portion of the output waveguide and the optical spectralshape from the arrayed waveguide grating;

FIGS. 7 to 10 are drawings showing general spectrum shapes other thanparabola shapes;

FIG. 11 is a sectional view showing the construction of an arrayedwaveguide grating module using the first embodiment arrayed waveguidegrating described above;

FIG. 12 is a plan view showing the metal plate with the temperaturesensor buried therein;

FIG. 13 is a block diagram showing an essential part of an opticalcommunication device using an arrayed waveguide grating as a secondembodiment of the present invention;

FIG. 14 is a block diagram showing an essential part of the opticalcommunication device shown in FIG. 13;

FIG. 15 is a graph for describing the relation between the currentoutput of the first and second photo-diodes as a result of the lightsignal reception and the computation result obtained in the computingcircuit in the second embodiment;

FIG. 16 is a block diagram showing the construction of an opticalcommunication system as a third embodiment of the present invention;

FIG. 17 is a block diagram showing the construction of the nodes in thethird embodiment;

FIG. 18 is a plan view showing the overall construction of a prior artarrayed waveguide grating;

FIG. 19 shows the construction of a prior art arrayed waveguide gratingcapable of selected wavelength compensation;

FIG. 20 shows the construction of another prior art arrayed waveguidegrating capable of selected wavelength compensation;

FIG. 21 shows an example of the spectrum shape of the light signaloutputted from the arrayed waveguide grating; and

FIG. 22 shows a different example of the spectrum shape of the lightsignal outputted from the arrayed waveguide grating.

PREFERRED EMBODIMENTS OF THE INVENTION

Preferred embodiments of the present invention will now be describedwith reference to the drawings.

FIG. 1 shows an arrayed wavelength grating as a first embodiment of thepresent invention. This arrayed waveguide grating 101 comprises, formedon a substrate 102, one or more input waveguides 103, a plurality ofoutput waveguides 104, one or more wavelength compensation outputwaveguides 105 disposed adjacent to the output waveguides 104, a channelwaveguide array 107 including a plurality of waveguides with lengthsprogressively increasing by a predetermined waveguide length difference,an input side slab-waveguide 108 inter-connecting the input waveguides103 and the channel waveguide array 107, and the output sideslab-waveguide 109 inter-connecting the channel waveguide array 107, theoutput waveguides 104 and the wavelength compensation output waveguides105. A multiplexed light signal inputted from the input waveguide orwaveguides 103 is expanded as it passes therethrough and then inputtedto the channel waveguide array 107. The incident light level is not thesame at the individual light incidence positions of the channelwaveguide array 107, but it increases as one goes toward the center andis substantially in Gauss distribution.

The channel waveguide array 107 has waveguides with such lengths that apredetermined waveguide length difference is provided between adjacentones, that is, the lengths progressively increase or decrease by thatdifference. Thus, the lights passing through the individual arraywaveguides reach the output side slab-waveguide 109 at predeterminedphase difference intervals. Actually, wavelength dispersion is present,and the in-phase plane is tilted in dependence on the wavelength.Consequently, the lights are focused (or converged) at positions varyingwith the wavelength on the interface between the output sideslab-waveguide 109 and the output waveguides 104 and wavelengthcompensation output waveguide 105. The output waveguides 104 aredisposed at positions corresponding to respective wavelengths. Thewavelength compensation waveguide 105 is used for center wavelengthdetection and compensation. It is thus possible to take out a givenwavelength component from the output waveguides 104. The wavelengthcompensation output waveguide 105 is used for center wavelengthdetection and compensation. The wavelength compensation output waveguide105 is used for wavelength compensation to set the wavelengths taken outfrom the output waveguides 104 to respective desired values.

FIG. 2 shows, to an enlarged scale, the neighborhood of the outputterminal of the output side slab-waveguide in the arrayed waveguidegrating of this embodiment. The plurality of output waveguides 104 whichare actually used for product and the output waveguide 105 which areused only for wavelength compensation are connected to the output side(right lower side in the Figure) of the output side slab-waveguide 109.The output waveguides 104 have parabolically flaring connectingportions. The wavelength compensation output waveguide 105, on the otherhand, has a tapering connecting portion.

FIGS. 3(a) to 6(b) show various shapes of connecting portions of theoutput waveguides in the neighborhood of the output terminal of thegeneral output side slab-waveguide and the spectrum shapes of the lightsignal output from the arrayed waveguide grating. FIG. 3(a) shows astate that an output waveguide 111 having the same shape as thewaveguide compensation output waveguide 105 shown in FIG. 2 is connectedto the output side of the output side slab-waveguide 109. In thisexample, the output waveguides 111 each have a tapering connectingportion. Thus, the solid curve spectrum shape of the light signal shownin FIG. 3(b) is sharper than the dashed curve reference spectrum shape.Generally, the thinner the connecting portion of the output waveguide111, the spectrum shape of the corresponding light signal outputted fromthe arrayed waveguide grating is the sharper. However, with a connectingportion having a sharpness exceeding a certain extent, the spectrumshape rather turns to a dull shape.

FIG. 4(a) shows a state that straight output waveguides 112 having afixed width are connected to the output side of the output sideslab-waveguide 109. In this case, the spectrum shape as shown in FIG.3(b) is obtained. This spectrum shape is the same as the dashed curvereference spectrum shape shown in FIG. 3(b).

FIG. 5(a) shows a state that output waveguides 113 having connectingportions flaring with a slight angle are connected to the output side ofthe output side slab-waveguide 109. In this example, the solid curvespectrum shape as shown in FIG. 3(B) is obtained. This shape is broaderthan the dashed curve reference spectrum shape.

FIG. 6(a) shows a state that output waveguides 114 having a shape likethe output waveguides 104 shown in FIG. 2 are connected to the outputside of the output side slab-waveguide 109. In this case, the solidcurve spectrum shape as shown in FIG. 6(b) is obtained. This spectrumshape, compared to the dashed curve reference spectrum shape, is dullwith a flat top. Although this flat top spectrum shape is excellent forthe purpose of making the loss variations in the ITU grid band as lessas possible, its top portion has no substantial great level variation.With this spectrum shape, therefore, it is difficult to detect thecenter wavelength, resulting in center wavelength compensation accuracydeterioration. For the center wavelength detection purpose, the solidcurve spectrum shape as shown in FIG. 3(b) obtainable by using thetapered output waveguides 111 as shown in FIG. 3(a) is most preferred.

As will be understood from the above considerations, in the output sideslab-waveguide 109 in the embodiment shown in FIG. 2 a preferredspectrum shape is obtainable with the plurality of output waveguides 104in the state of use of the product. The wavelength compensation outputwaveguide 105 permits obtaining a preferred spectrum shape for thedetection and high accuracy compensation of the center wavelength. Asfor the spectrum shape of the light signal outputted from the wavelengthcompensation output waveguide 105 the shape of the neighborhood of theportion connected to the output side slab-waveguide 109 can be contrivedto obtain spectrum shapes similar to a shape other than such parabolicshape, and among such spectrum shapes those suited for the wavelengthcompensation output waveguide 105 can be selected.

FIGS. 7 to 10 show general spectrum shapes other than polabola shapes.These spectrum shapes will now be described in view of the centerwavelength detection. The shape shown in FIG. 7 has two, i.e., a higherand a lower level, peaks 121 and 122, and it is thus asymmetric as awhole. Therefore, it is difficult to specify the center wavelength inthis shape. The shape shown in FIG. 8 has two peaks 123 and 124 of thesame level. The bottom position 125 between the two peaks may correspondto the center wavelength. In this case, however, it is difficult tospecify the center wavelength because of the presence of a plurality ofsame level points. Particularly, as shown FIG. 8, the bottom portion 125may be deviated from the two peaks 123 and 124. In this case, the bottomportion 125 is no longer the center wavelength position.

FIG. 9 shows a triangular spectrum shape. In such shape constituted bystraight ascending and descending portions, it is ready to detect thecenter wavelength. FIG. 10 shows a spectrum shape having straight risingand falling portions. With such shape, it is possible to relativelyreadily calculate the half value width. Ready center wavelengthcalculation is obtainable even if the flat portion length (i.e.,spectrum width) is relatively large. Of course, with a short flatportion length, the accuracy of the center wavelength detection is high.

FIG. 11 shows the summary of the construction of an arrayed waveguidegrating module using the first embodiment arrayed waveguide gratingdescribed above. The arrayed waveguide grating module 201 as illustratedcomprises a box-like case 202, a temperature control element 203constituted by a Velch element disposed on the bottom of the case 202for heating or cooling the same, an arrayed wavelength grating 101 and ametal plate 205 intervening between the arrayed waveguide grating 101and the temperature control element 203. In this embodiment, a high heatconductivity copper plate is used as the metal plate 205. The metalplate 205 has a size greater than the size of contact with thetemperature control element 203 for enlarging the temperature controlregion thereof.

The metal plate 205 has a groove, in which a temperature sensor 206 isburied together with the a high heat conductivity material 207. Thedetected temperature signal is inputted to a temperature control circuit209 for controlling the temperature of the temperature control element203. The temperature sensor 206 buried in the metal plate 205 is led outfrom a position 209. In this embodiment, a thermistor is used as thetemperature sensor 206.

Optical fibers 211 to 213 are led out from the side of the inputwaveguides 103 of the arrayed waveguide grating 101 shown in FIG. 1 andthe side of the output waveguides 104 and wavelength compensation outputwaveguide 105 to the outside of the case 20. Of these optical fibers,the optical fiber 211 has one terminal connected to the input waveguides103 and the other terminal connected to the light source side (notshown). The optical fiber 212 has one terminal connected to the outputwaveguides 104 and the other terminal connected to a circuit part (notshown) for processing demultiplexed light signals. The remaining opticalfiber 213 has one terminal connected to the wavelength compensationoutput waveguide 105 and the other terminal connected to a wavelengthdetection circuit (not shown).

FIG. 12 shows the metal plate with the temperature sensor buriedtherein. The metal plate 205 has a temperature detection region 221shown enclosed in the dashed rectangle, which is in contact with thechannel waveguide array 107 and the input and output sideslab-waveguides 108 and 109 in the arrayed waveguide grating 101 shownin FIG. 1. By detecting the temperature of this region 221 with highaccuracy and controlling the detected temperature to a predeterminedtemperature, it is possible to prevent characteristic changes due totemperature variations in the arrayed waveguide grating 101.

The metal plate 205 has a groove 222 formed in its front surface, andthe temperature sensor 206 is buried together with the high heatconductivity material 207 in the groove 222. The temperature sensor 206has a temperature detecting portion 223, which is located at one end ofit and buried in the substantial center of the temperature detectingregion 221. From this position, a pair of lead lines 225 and 226 are ledin a spiral fashion in the metal plate 205 and to the outside from theposition 209. The pair lead lines 225 and 226 are relatively thin wires.

In such arrayed waveguide grating module 201, the optical fiber 211shown in FIG. 11 is connected to a monitor light source (not shown), andthe optical fiber 13 is connected to the wavelength detection circuit(not shown). Then, the control temperature is set in the temperaturecontrol circuit 208 such that the wavelength detected in the wavelengthdetection circuit has a predetermined value. The wavelength compensationoutput waveguide 105 and the output waveguides 104 are designed suchthat the wavelengths inputted to them are in a predetermined relation.Thus, with the detection of the temperature of the metal plate 205 andthe control of the detected temperature of the metal plate 205 in thetemperature control circuit 208 such that the light led out from thelight source and through the wavelength compensation output waveguide105 has a predetermined wavelength, a light signal having a desiredwavelength is inputted to each of the output waveguides 104.

When the ambient temperature is changed from the initial presettemperature, the arrayed waveguide grating 101 and the temperaturesensor 206 receive thermal feedback such as to reflect the externaltemperature. In consequence, the operating point is usually deviatedfrom the initial preset temperature. In this embodiment arrayedwaveguide grating module 201, however, the temperature detecting portion223 of the temperature sensor 206 is buried in the metal plate 205, andthe groove 222 is closed by the arrayed waveguide grating 101.Furthermore, as shown in FIG. 12, the pair lead lines 225 and 226 whichare liable to provide thermal feedback to the temperature detectingportion 223 are buried together with the high heat conductivity material207 in the metal plate 205. Moreover, the lead lines 225 and 226 are notled out through the metal plate 205 from the position of the temperaturedetecting portion 223 in a shortest distance fashion, i.e., a straightfashion, but are led out in a sort of spiral fashion as one form ofcurve to cover an increased distance.

Thus, the ambient temperature can not be fed back from the position 209along the lead lines 225 and 226 to the temperature detecting portion223, but the heat energy corresponding to the change in temperature isabsorbed in the metal plate 205 itself through the lead lines 225 and226 therein, which cover a relatively long distance. The metal plate 205itself is temperature controlled by the temperature control element 203to a predetermined temperature. Thus, the effects of the ambienttemperature from the position 209, like the effects of the ambienttemperature in the other portion of the metal plate 205 surrounding thetemperature control element 203, are weakened as one goes inwardly ofthe metal plate 205. In the temperature detecting region 221 which islocated in the neighborhood of the center of the metal plate 205, thetemperature of the lead lines 225 and 226 thus becomes substantially thesame as the temperature of metal in that portion. In practice, theambient temperature can not be thought to be fed back to the temperaturedetecting portion 223.

For the above reason, in the arrayed waveguide grating module 201 thetemperature detecting portion 223 can accurately measure the temperatureof the portion of the arrayed waveguide grating 101 corresponding to thetemperature detection region 221 without being adversely affected by theambient temperature. It is thus possible to realize stable temperaturecontrol at all times irrespective of ambient temperature changes.

FIG. 13 shows an essential part of an optical communication device usingan arrayed waveguide grating as a second embodiment of the presentinvention. In this optical communication device 301, the arrayedwaveguide grating 11 shown in FIG. 1 as the first embodiment is used. Anoptical fiber 302 having one terminal connected to a light source (notshown) has the other terminal connected to the input side of the arrayedwaveguide grating 101. To the output side of the arrayed waveguidegrating 101 are connected optical fibers 303 corresponding to the outputwaveguides 104 (see FIG. 1) and an optical fiber 304 corresponding tothe wavelength compensation output waveguide 105 are connected. Denotingthe wavelength of a light signal outputted from the light source (notshown) by λ₀, lights of wavelengths λ₁ to λ_(n) are outputted from theoptical fiber 303. A light of wavelength λ_(m) is outputted from theoptical fiber 304.

An output monitoring controller 306 is connected to the output side ofthe optical fiber 304. The output monitoring controller 306 outputs amonitor signal 307 which is inputted to a temperature control circuit308. The temperature control circuit 308 holds the wavelengths of thelight signals outputted from the optical fiber 303 to desired values atall times by controlling the temperature of the arrayed waveguidegrating 101.

FIG. 14 specifically shows an essential part of the opticalcommunication device shown in FIG. 13. As shown, the output monitoringcontroller 306 a Mach zender circuit 323 as a two-output interferometerfor receiving the a laser light 322 of wavelength λ_(m) outputted fromthe arrayed waveguide grating 101, a first and a second photo-diode 326₁ and 326 ₂ for receiving a first and a second laser beam signal 324 ₁and 324 ₂, respectively, outputted in respective directions from theMach zender circuit 323, and a computing circuit 328 for computingreception outputs 327 ₁ and 327 ₂ from the photo-diodes 326 ₁ and 326 ₂.The computation result output 329 of the computing circuit 328 isinputted to the temperature controller 308. The wavelength of thearrayed waveguide grating 101 is controlled to a desired value accordingto the temperature control output 332 of the temperature control circuit308. The wavelength control may also be obtained by controlling a drivecurrent in a laser diode (not shown) as a component of the arrayedwaveguide grating 101.

In the second embodiment, the Mach zender circuit 323 is a single-sideinput/output terminal interferometer. Although the Mach zender circuit323 of single-side input/output terminal interferometer is by no meanslimitative, compared to the arrangement with the input and outputterminals disposed in the opposite sides, the use of the single-sideinput/output interferometer, in which not only the input terminal butalso the output terminal is disposed on one side of the circuit, maycontribute to the module size reduction. In addition, the arrangement inwhich the optical path difference between the input and output terminalsis obtained in a figure R curved portion, is desired from the standpointof the element size reduction.

FIG. 15 is a graph for describing the relation between the currentoutput of the first and second photo-diodes as a result of the lightsignal reception and the computation result obtained in the computingcircuit. With light frequency changes, the current as the receptionoutput 327 ₁ of the first photo-diode 326 ₁ is changed as a sinusoidalwave in a predetermined cyclic free spectral range (hereinafter referredto as FSR) having a cycle period corresponding to one cycle of the losswavelength characteristic. The current as the reception output 327 ₂ ofthe second photo-diode 326 ₁ is changed likewise as 180-degreeout-of-phase output. This embodiment of the device is designed such thatthese currents are equal to that in the ITU grid with the cyclic FSRpredetermined by ITU (International Telecommunication Unison).

Since the reception outputs 327 ₁ and 327 ₂ of the first and secondphoto-diodes 326 ₁ and 326 ₂ are 180-degree out-of-phase with eachother, denoting these currents by I_(PD1) and I_(PD2), respectively,their sum is fixed irrespective of the light signal frequency.

The computing circuit 328 computes the ratio A between the currentI_(PD1) as the reception output of the first photodiode 326 ₁ and thesum of the currents I_(PD1) and I_(DP2), as given by the followingequation 2.

A=I _(PD1)/(I _(PD1) +I _(PD2))  (2)

The arrayed waveguide grating 101 outputs the temperature control signal332 such that the ratio A has a predetermined value at all times. Thetwo currents I_(PD1) and I_(PD2) are changed periodically with aninterval of one cycle or longer. It is thus possible to set apredetermined wavelength in a broad wavelength range. For example, bysetting the temperature of the arrayed waveguide grating 101 to theneighborhood of t₁, the wavelength λ_(m) of the laser beam signal 322can be held at a particular light signal wavelength f₁ or apredetermined neighborhood light frequency. Also, by controlling thetemperature of the arrayed waveguide grating 101 to a differenttemperature in the neighborhood of t₂ from t₁, it is possible to providethe output with a different light wavelength in the neighborhood of f₂as the laser beam signal 322 and hold the light frequency of this signalat f₂ or a predetermined neighborhood light frequency thereof.

Particularly, highly accurate wavelength control is possible by settingthe light signal frequency as subject of control at a desired positioncorresponding to sharply tilted positions of the curves representing thecurrents I_(PD1) and I_(PD2) shown in FIG. 15. As an example, wavelengthλ_(m) in FIG. 5 is assumed to be the subject of control. In thisassumption, the points on the curves of the currents I_(PD1) and I_(PD2)corresponding to the wavelength λ_(m) are operating points 341 and 342.Also, the points on the curves of the currents I_(PD1) and I_(PD2)corresponding to a wavelength (λ_(m)+Δλ) deviated by a slight amount Δλto the longer wavelength side are operating points 343 and 344.

In this case, by denoting the current difference between the twooperating points 341 and 343 by ΔP, the ratio A shown in the equation(2) is P/(I_(PD1)+I_(PD2)). In sharply tilted portions of the curves ofthe currents I_(PD1) and I_(PD2), the difference ΔP takes a relativelylarge value, and the wavelength of the laser beam signal 322 can behighly accurately set to the neighborhood of the wavelength λ_(m).

Considering one cycle FSR of the sinusoidal wave shown in FIG. 15, thewave curve has two further points 345 and 346 corresponding to entirelythe same levels of the currents I_(PD1) and I_(PD2) as the respectivetwo operating points 341 and 342. These points correspond to thewavelength deviation by one half of the cycle FSR. At these two points345 and 346, however, the sign of the current I_(PD1) as the nominatorin the equation (2) when the wavelength is increased or reduced by Δλ isopposite. The computation result is thus different, and it is possibleto specify the wavelength of the control subject in the wavelength rangecorresponding to one FSR cycle of the sinusoidal wave.

FIG. 16 shows a summary of the construction of an optical communicationsystem as a third embodiment of the present invention. In this opticalcommunication system, light signals of N channels of waveguides λ₁ toλ_(N) outputted to an optical transmitter connected to an SONET(Synchronous Optical Network) system (not shown) provided on thetransmission side, are multiplexed in an optical multiplexer (MUX) 402,then amplified in a booster amplifier 403 and then outputted to an lightsignal transmitting line 404. The wavelength multiplexed light signal405 is adequately amplified in an in-line amplifier 406, and then ledthrough a pre-amplifier 407 to an optical demultiplexer (DMUX) 408 fordemultiplexing to separate the initial wavelengths λ₁ to λ_(N), whichare received in an optical receiver 409. On the light signaltransmitting line 404, a suitable number of nodes (OADM) 411 ₁ to 411_(M) are disposed. Light signals of desired wavelengths are inputted toand outputted from the nodes 411 ₁ to 411 _(M). The opticaldemultiplexer 408 is constituted by the arrayed waveguide grating 101 asshown in FIG. 1.

FIG. 17 shows a summary of the construction of the nodes. Here, thefirst node 411 ₁ is shown (SEE FIG. 16), but the second to M-th modes411 ₂ to 411 _(M) also have the same construction. The signal from thelight signal transmitting line 404 shown in FIG. 23 is inputted to aninput side arrayed waveguide grating 421 in the first node 411 ₁ fordemultiplexing to separate light signals in N channels of wavelengths λ₁to λ_(N). The separated light signals of the wavelengths λ₁ to λ_(N) aredropped by two-input two-output optical switches 422 ₁ to 422 _(N),which are each provided for each of wavelengths λ₁ to λ_(N), to the nodeside receiver 426. Also, light signals transmitted from the wavelengthλ₁ to λ_(N) are added from a node side transmitter 424. The outputs ofthe two-input two-output optical switches 422 ₁ to 422 _(N) are gaincontrolled in respective attenuators (ATT) 427 ₁ to 427 _(N) andinputted to an output side arrayed waveguide grating 428. The outputside arrayed waveguide grating 428 is an element having constructioninverse to the output side arrayed waveguide grating 421, and itmultiplexes the light signals in the N channels of the wavelengths λ₁ toλ_(N) to output the light signal 405 obtained by the multiplexing to thelight signal transmitting line 404.

As shown above, the first node 411 ₁ shown in FIG. 17 and also thesecond to M-th nodes 411 ₂ to 411 _(M) and the optical demultiplexer 408all use the arrayed waveguide grating 101 shown in FIG. 1. The abovelight signal of the wavelength λ_(m) outputted from the output sidewaveguide (i.e. monitor signal waveguide) when monitor light signal isinputted from input side waveguide, is progressively monitored forwavelength compensation of the output side waveguides, from which thelight signals of the wavelengths λ₁ to λ_(N) are outputted. To this end,as shown in FIG. 16, the nodes 411 ₁ to 411 _(M) and the opticalreceiver 409 are provided with output monitor controllers 431 ₁ to 431_(M) and 431 _(R), respectively.

The arrayed waveguide grating 101, even when it is used as multiplexer,can do wavelength compensation likewise by inputting the monitor lightsignals from the intrinsic output side waveguides and progressivelymonitoring the light signal of the wavelength .m outputted from theintrinsic input side waveguides (i.e., monitor light signal waveguides).Although not shown in this embodiment, it is further possible to obtaincompensation with respect to the arrayed waveguide grating 101 on theside of the output side arrayed waveguide grating 428 in the opticaltransmitter 401 and the nodes 411 ₁ to 411 _(M). To this end, outputmonitoring controllers may be provided.

In the above second embodiment, the wavelength compensation is performedby making wavelength measurement with the output monitoring controllerusing the Mach zender circuit and two diodes, it is also possible tomake wavelength compensation of an arrayed waveguide grating or anarrayed waveguide grating module by using a wavelength meter and hencethe result output thereof.

As has been described in the foregoing, according to the first to eighthand twenty sixth to thirty third aspects of the present invention, thesecond waveguide provided as at least one of the output waveguides isdifferent from the first waveguides, and it is thus possible to obtainmeasurement, which is different from the measurement in the case ofusing the first waveguides. By using the result of this measurement, itis possible to make more accurate center wavelength compensation of eachwaveguide of the arrayed waveguide grating.

Particularly, according to the fourth and twenty ninth aspects of thepresent invention, the spectrum of the light signal outputted from thesecond output waveguide as one of the output waveguides can be held withless loss variation state because of its narrow spectral width comparedto the spectrum of the light signals outputted from the first outputwaveguides.

According to the fifth and thirteenth aspects of the present invention,the spectrum of the light signal outputted from the second outputwaveguide has a sharp peak compared to the case of the usual waveguidesas the output waveguides, and thus it can be readily specified.

According to the sixth to eighth and thirty first to thirty thirdaspects of the present invention, only the portion of the monitor lightsignal output waveguide on the side thereof connected to the output sideslab-waveguide is made different from the case of the first outputwaveguides. This arrangement thus can not only be readily provided butalso permits variously contriving the spectrum shape and received lightsignal level.

According to the ninth, tenth, thirty fourth and thirty sixth aspects ofthe present invention, the arrayed waveguide grating module isconstructed by assembling the arrayed waveguide grating together withother components. Thus, unlike the case of, for instance, assembling thearrayed waveguide grating such as to permit the wavelength compensationitself to be made within the module, it is possible to obtain sucheffects as obtaining an efficient component arrangement in the moduleitself or saving the space of disposition of a plurality of components.Furthermore, by assembling precise components, it is possible to improvethe accuracy of the wavelength compensation or stabilizing the productquality.

According to the eleventh to fifteenth and thirty sixth to fortiethaspects of the present invention, the wavelength compensation withrespect to the light signals outputted from the first waveguides at thetime of the input of the light signals from the input waveguides, isperformed by inputting the monitor light signal to the arrayed waveguidegrating module and detecting the monitor light signal outputted from theexclusive monitor light signal waveguide. Thus, the wavelengthcompensation processing is possible even in the state of use of thefirst waveguides.

In the optical communication device according to the sixteenth,seventeenth, twenty fourth, twenty fifth, forty first, forty second,forty ninth and fiftieth aspects of the present invention, at the timeof the arrayed waveguide grating module check the arrayed waveguidegrating can be adjusted by inputting the monitor light signal forchecking from either one of the input waveguides such that the monitorlight signal outputted from the monitor light signal waveguide has apredetermined wavelength, and a signal processing using the wavelengthcompensated light signals outputted from the first waveguides of thearrayed waveguide grating can be started by inputting the actually usedlight signals from the input waveguides of the adjusted arrayedwaveguide grating module.

According to the eighteenth to twenty third and forty third to fortyeighth aspects of the present invention, the wavelength of the componentconstituted by the arrayed waveguide grating is compensated for. It isthus possible to obtain highly reliable satisfactory communication.Particularly, according to the twenty fourth aspect of the presentinvention, no expensive wavelength meter is used, and it is thuspossible to reduce cost of the optical communication system itself.

Changes in construction will occur to those skilled in the art andvarious apparently different modifications and embodiments may be madewithout departing from the scope of the present invention. The matterset forth in the foregoing description and accompanying drawings isoffered by way of illustration only. It is therefore intended that theforegoing description be regarded as illustrative rather than limiting.

What is claimed is:
 1. An arrayed waveguide grating module comprising:an arrayed waveguide grating including one or more input waveguides, aninput side slab-waveguide connected to the output side of the inputwaveguide or waveguides, a plurality of arrayed waveguides formed on theside of the input side slab-waveguide opposite the input waveguide orwaveguides, an output side slab-waveguide connected to the otherterminal of the arrayed waveguides, a plurality of first outputwaveguides connected to the output side slab-waveguide on the sidethereof opposite the arrayed waveguides and at least one second outputwaveguide formed together with the first output waveguides on the sideof the output side slab-waveguide opposite the arrayed waveguides, theafore-said components being all formed on a substrate and the opticalspectrum outputted from the second output waveguide being different fromthe optical spectra outputted from the other output waveguides; andoptical fibers each having one terminal optically connected to at leastpart of the plurality of waveguides constituting the output waveguidesof the arrayed waveguide grating.
 2. An arrayed waveguide grating modulecomprising: an arrayed waveguide grating including one or more inputwaveguides, an input side slab-waveguide connected to the output side ofthe input waveguide or waveguides, a plurality of arrayed waveguidesformed on the side of the input side slab-waveguide opposite the inputwaveguide or waveguides, an output side slab-waveguide connected to theother terminal of the arrayed waveguides, a plurality of first outputwaveguides connected to the output side slab-waveguide on the sidethereof opposite the arrayed waveguides and at least one second outputwaveguide formed together with the first output waveguides on the sideof the output side slab-waveguide opposite the arrayed waveguides, theafore-said components being all formed on a substrate and the shape ofthe connecting portion of the second output waveguide with respect tothe output side slab-waveguide being different from the shape of theconnecting portion of the second output waveguides with respect to theoutput side slab-waveguide; and optical fibers each having one terminaloptically connected to at least part of the plurality of waveguidesconstituting the output waveguides of the arrayed waveguide grating. 3.An arrayed waveguide grating module comprising: an arrayed waveguidegrating including at least one input waveguides, an input sideslab-waveguide with the input side thereof connected to the output sideof the input waveguide or waveguides, a channel waveguide arrayincluding a plurality of waveguides with lengths progressivelyincreasing by a predetermined waveguide length difference, the inputside of the waveguides being connected to the output side of the inputside slab-waveguide, an output side slab-waveguide with the input sidethereof connected to the output side of the plurality of waveguidesconstituting the channel waveguide array and a plurality of outputwaveguides each having one terminal connected to the output side of theoutput side slab-waveguide, the optical spectrum of the light outputtedfrom a second waveguide as one of the output waveguides being differentfrom the optical spectrum of the lights outputted from first waveguidesas the remaining output waveguides; and optical fibers each having oneterminal optically connected to at least part of the plurality ofwaveguides constituting the output waveguides of the arrayed waveguidegrating.
 4. An arrayed waveguide grating module comprising: an arrayedwaveguide grating including at least one input waveguides, an input sideslab-waveguide with the input side thereof connected to the output sideof the input waveguide or waveguides, a channel waveguide arrayincluding a plurality of waveguides with lengths progressivelyincreasing by a predetermined waveguide length difference, the inputside of the waveguides being connected to the output side of the inputside slab-waveguide, an output side slab-waveguide with the input sidethereof connected to the output side of the plurality of waveguidesconstituting the channel waveguide array and a plurality of outputwaveguides each having one terminal; connected to the output side of theoutput side slab-waveguide, a connecting portion of the second outputwaveguide with respect to the output side slab-waveguide having a shapedifferent from the shape of connecting portions of the first outputwaveguides with respect to the output side slab-waveguide; and opticalfibers each having one terminal optically connected to at least part ofthe plurality of waveguides constituting the output waveguides of thearrayed waveguide grating.